Min/Max Boards

Augment Elemental (Magic of Eberron): Makes your elementals better, with temporary HP and attack and damage bonuses.. Not the best choice for a Malconvoker, unless you alter the class to work on neutral summons - in which case, it becomes a great choice.

Augment Summoning (PHB): Probably your most important feat, as it gives +4 STR and CON to all your summons, making them more effective in melee and more durable. Requires the comparatively less useful Spell Focus (conjuration), but you can always take the Enhanced Summoning Alternative Class Feature to trade Scribe Scroll for this. At least, a wizard can.

Beckon the Frozen (Frostburn): A minor damage boost (1d6 cold) and the addition of the Cold subtype on your summons. This opens up a few buffs from the same book for your creatures, but beware their new vulnerability to fire. Optional to use, so don't when it's disadvantageous.

Chain Spell (Complete Arcane): While you can only chain single-target spells that have a range greater than touch, this is a great metamagic for spreading buffs around. Secondary uses allow you to toss out widespread devastation on the battlefield, so I highly recommend picking it up. It's expensive though, at +3.

Cloudy Conjuration (Complete Mage): So many tactical possibilities for a cloud of sight-blocking, sickening smoke. Put it between you and your enemies when you summon to gain concealment and break line of sight for enemy targeting. Put it on blindsighted summons to give your enemies a temporary debuff while keeping your allies in the fight. Teleport your minions around and leave waves of divisive black smoke. One of my favorite feats, and an auto-include in nearly every summoning build.

Demon Mastery (FCI): +1 CL when summoning demons and +2 on CHA checks to bind them. Good for a demonic-focused summoner. Easy to alter for your own purposes, becoming Devil Mastery, Yugoloth Mastery, et cetera.

Extend Spell (PHB): Likely one of your first metamagics. Always useful, though as a Malconvoker you'll get it for free.

Fiendish Summoning Specialist (Planar Handbook): Allows you to freely add one evil creature per spell level to your summoning lists. Handy if your DM is a stickler about what you can summon. There's also a Celestial version of this, if you're so inclined.

Imbue Summoning (PHB II): A +1 metamagic, this spell allows you to enhance your summons with a 3rd-level-or-lower buff spell for free at the time of summoning. Has to have a range of Touch, though, which can be limiting. A few suggestions from Akalsaris: Babau Slime, Heroics, Girallon's Blessing, Cat's Grace, Eagle's Splendor, or Heroism.

Infernal Bargainer (Races of Faerun): It's a regional feat, and only available to Outsiders. But it adds 2 HD to your binding limits and a -2 on all attempts to escape from your traps. Makes you that much better of a binder. Minor bonuses on a few interplanar divinations, too.

Infernal Sorcerer Heritage (PHB II): Sorcerer-only. Gives +2 to CL when summoning evil outsiders, and minor save bonuses against fire and poison.

Invisible Spell (Cityscape): If you can slide it past your DM (because it's pretty cheesy), all of your summons are now invisible. For free.

Metamagic School Focus (Complete Mage): 3/day, reduce the level adjustment of metamagic in the chosen school by one. Handy.

Nexus Method (Dragon #319): Regional Greyhawk feat, Wizard-only. Lets you spontaneously change non-Conjuration spells to Summon Monster spells. Useful if you're a generalist summoner or a specialist in something other than Conjuration - not so useful as a Conjurer, since most of your slots will be in the school anyway. Definitely avoid as a Focused Specialist Conjurer.

Practiced Spellcaster (Complete Arcane): Fix that lost caster level from the Malconvoker or other partial-progression PrC.

Rapid Metamagic (Complete Mage): Mainly for Sorcerer entry. Apply metamagic to your summoning and still keep it down to a full round action.

Rapid Spell (Complete Divine): Gets those full-round actions down to standards for a +1 metamagic. Good for divine entry, since wizards have the Rapid Summoning ACF and Sorcerers can take Rapid Metamagic.

Stalwart Planar Ally (Planar Handbook): Though you need a Touchstone feat first, this gives you an auto-extend, +4 AC, and +4 to all saves on any creature you summon native to the same plane as your touchstone. Baator or the Abyss are good choices.

Summon Elemental (Complete Mage): Treantmonklvl20 has written more elegantly about this feat on his guide. This gives you free, unlimited elemental summoning, more handy for utility than for combat but still just about one of the most versatile feats around. Nearly always an auto-include.

Twin Spell (Complete Arcane): For a +4 adjustment, you can now summon twice the creatures. With Infernal Legion, a ninth level spell could potentially get you eight Voors (if you roll well). Dubiously useful, but an awfully cool trick.

Player's Handbook

Player's Handbook II

Spell Compendium

While not directly making you or your summons better, there are three skill tricks I'll nearly always take, just because they're useful and the investment is fairly minor.

Collector of Stories: A +5 bonus to identify creatures is really useful to you, as knowing your extraplanar creatures is key to success. You can't call one up you don't know about, for example. Makes a lot of sense fluff-wise, too, as you can be a walking encyclopedia of planar monstrosities.

Conceal Spellcasting: Always, always get this if you can spare the points in Sleight of Hand. Hiding your spellcasting has so many uses. No attacks of opportunity, for example. A sneaky summoner is a living summoner.

Swift Concentration: Though as with Extraordinary Concentration in the Feats section above this is questionably legal, this trick allows you to maintain concentration (say, on an Elemental Monolith) as a swift action, opening up the rest of your turn for more summoning.

Admiral's Bicorne (Stormwrack, 51,000 gp): Quite possibly my favorite item ever. While its +5 to Profession (sailor) checks doesn't help you much, the +5 untyped bonus to all charisma checks does, and it also gives you and all your allies a +2 morale bonus on attack rolls, skill checks, and saves. That's a potent buff right there - not only does it make your summons more effective in combat, but it also makes you better too, as well as increasing your Bluff checks by a hefty amount. It's also quite useful for binding, as the battle of wills involved is in fact a charisma check.

Choker of Eloquence, Greater (Complete Adventurer, 24,000 gp): +10 to Bluff checks. Need I say more? Gives the same bonus to Diplomacy and Perform (sing), but you probably don't care about that too much.

Circlet of Persuasion (Dungeon Master's Guide, 4,500 gp): Successfully binding a creature requires a Charisma check. This item gives you +3 to such checks. Competes for space with the Headband of Intellect, but still handy (especially if relegated to another item slot).

Cloak of Charisma +2/+4/+6 (DMG, 4,000-36,000 gp): Most important for Cha-based summoners, but also handy to increase Bluff and Charisma checks even for shut-in antisocial wizards who dumped it at chargen.

Headband of Intellect +2/+4/+6 (DMG, 4,000-36,000 gp): Obvious, but still useful. Crucial for wizards and/or archivists.

Mask of Lies (Magic Item Compendium, 4,500 gp): That +5 competence bonus to Bluff is always handy for a Malconvoker, and having your alignment undetectable can definitely sidestep problems with fiends who can detect good. Disguise Self is just gravy.

Masterwork Tools (DMG, 50 gp each): Always handy - that +2 bonus isn't much by itself, but it helps. I like a bound encyclopedia set, one for each Knowledge skill: only costs 500 gp. Getting one for Bluff, Concentration, and/or Spellcraft should also be high on your list. The disadvantage is that each one weighs a pound, and lots of them add significant weight to your likely-low-strength caster.

Periapt of Wisdom +2/+4/+6 (DMG, 4,000-36,000 gp): Important for cleric/archivist entry - stat boosting items shouldn't really need to be mentioned, but I do so for completion's sake.

Ring of Mighty Summons (Complete Mage, 14,000 gp): Three times per day, you can summon creatures with maximum hit points. This does however halve their duration, but as a Malconvoker (or with Extend Spell), you're breaking even.

Robe of Mysterious Conjuration (MIC, 10,000 gp): Not crucial, but handy: three times a day, you can spontaneously convert any spell into a summon monster spell of the same level. You likely won't be running out in the first place, but anything that increases your versatility with your summons is a good deal.

Scrolls of Uncertain Provenance (MIC, 8,000 gp): Though they have alignment restrictions (LG, LN, LE, or N), a +5 competence bonus to all Knowledge skills is great for monster identification.

Worldmeet Glade (CM, 18,000 gp): Though it's a magical location and not an item per se, it's a goddamn steal. It basically gives you a blanket untyped +2 bonus to nearly everything: HP per HD, attack and damage rolls, saves, skill checks, and ability checks. It's clearly overpowered (there are no restrictions on its usage per RAW), but a must-have for every summoner.

Aspect of Baphomet
CR: 7
HD: 8
How to get it: None by RAW, likely SM VII
Role: Brute
Fluff: Baphomet, the Prince of Beasts, is a savage demon lord who revels in carnage and bloodshed. Though the original possesses a scientific curiosity, his aspects are brutal and exist only to brawl. Baphomet despises Graz'zt and Yeenoghu.
Advantages: A decent combatant, with three acceptable attacks and good DR. A great charger. His taurian cunning gives him a few advantages, like immunity to Maze and tracking. One of the few fiends with ranks in Knowledge (nature).
Disadvantages: No SR. His iterative attacks aren't likely to hit.
Notable SLAs: None.
Final Evaluation: A capable brute, but little more. You probably have better choices in your repertoire.

Aspect of Dagon
CR: 9
HD: 9
How to get it: None by RAW, likely SM VIII
Role: Brute
Fluff: Dagon is one of the eldest demon lords, roaming the depths of his realm in search of knowledge and lore. His aspects are less scholarly, concentrating more on ripping apart foes or devouring them whole. Dagon has no real enemies amongst his demonic brethren.
Advantages: A capable grappler, with constricting tentacles or a bite that can swallow your foes. Good DR and Fast Healing. Form of Madness gives enemies penalties against aquatic foes - and guess who has the aquatic subtype?
Disadvantages: Though his abilities concentrate on grappling, his modifier is a bit disappointing for the level. Disappointing damage. No SR. His Form of Madness can also affect you.
Notable SLAs: None.
Final Evaluation: Eh. A bunch of grappling options, but not the modifier to back it up. His Form of Madness is a double-edged sword. I wouldn't risk it.

Aspect of Demogorgon
CR: 9
HD: 11
How to get it: None by RAW, likely SM VIII
Role: Manipulator
Fluff: Demogorgon is truly the Prince of Demons, bestial and cunning. His aspects are not quite as intelligent or adept with magic, but they do retain his dual nature and enchanting gaze. He is constantly at war with Orcus and Graz'zt.
Advantages: He can take two actions per round. His Gaze attacks can charm and confuse, and are at a respectable DC. Impressive knowledge skills.
Disadvantages: Pathetic damage. No SR.
Notable SLAs: None.
Final Evaluation: Having Charm Monster and Confuse on call as gaze attacks can handy, if somewhat circuitous. Aspects of Demogorgon won't be tearing anything to shreds anytime soon, quite unlike the original.

Aspect of Fraz-Urb'luu
CR: 7
HD: 9
How to get it: None by RAW, likely SM VII
Role: Caster
Fluff: A noted deceiver and summoner, Fraz-Urb'luu has only just returned to the Abyss from a long imprisonment. He is carefully rebuilding his power base. His aspects are not as cunning, but share his reliance on minions. Fraz-Urb'luu has no direct enemies, but few demon lords look upon him fondly.
Advantages: Can expand your mid-level summoning power with his SLAs and Summoning ability. Decent fly speed and good AC. Plenty of ranks in UMD.
Disadvantages: Unimpressive in melee and a bit fragile. No SR. As a summon, it's nearly useless.
Notable SLAs: Greater Teleport at will, plus Persistent Image and Summon Monster IV 3/day, plus Summon Monster V 1/day.
Final Evaluation: Much better as a bind, in which case it can use its summoning abilities. Persistent Image, like all illusions, is only limited by your creativity, giving ol' Fraz plenty of potential.

Aspect of Juiblex
CR: 8
HD: 8
How to get it: None by RAW, likely SM VII
Role: Brute
Fluff: Juiblex, the Faceless Lord, is the simplest demon lord to understand - he hates all living things and seeks only to engulf them into his oozing maw. His aspects are likely easily comprehensible. Juiblex maintains a healthy enmity for Zuggtmoy, as they share the same realm in the Abyss and war constantly.
Advantages: Decently mobile, what with being Amorphous. Good immunities. Decent grapple damage with his acidic slams. Blindsight 60'.
Disadvantages: Like Dagon, a disappointing grapple modifier makes the aspect of Juiblex a poor choice for doing practically the only thing he can. No SR.
Notable SLAs: None.
Final Evaluation: Just about on par with Dagon - though he does less damage, he can also grapple larger creatures. But they're both poor grapplers, and should be avoided.

Aspect of Kostchtchie
CR: 10
HD: 12
How to get it: None by RAW, likely SM VIII
Role: Brute
Fluff: The self-proclaimed ruler of all frost giants, Kostchtchie exists only to conquer all he can see. He has a healthy hatred for nearly everything, and only tolerates his frost giant supplicants. A bit dull for a demon lord, he's likely easily tricked. He maintains no specific rivalry with any other demon lord, but would rip any of them to pieces.
Advantages: A painful bruiser with his freezing iron maul. Immensely strong, he can knock around lesser creatures with ease or throw rocks from range.
Disadvantages: Low AC and DR that's slightly easier to bypass than other aspects.
Notable SLAs: None.
Final Evaluation: The Abyssal giant is essentially the same thing as an aspect of Kostchtchie, and it's only a level higher. It's also much better. But if you need to lay down some hammerin', he'll serve until the other giants are available.

Aspect of Malcanthet
CR: 8
HD: 9
How to get it: None by RAW, likely SM VII
Role: Assassin
Fluff: Malcanthet is the queen of the succubi, hedonistic and seductive. She exists only to indulge her own pleasures. While not as enchanting, her aspects are just as treacherous. She maintains an ongoing war with Yeenoghu and a rivalry with Graz'zt.
Advantages: 5d6 sneak attack damage on an adamantine spiked chain. A good fly speed and a WIS-draining poison. Good ranks in social skills and UMD.
Disadvantages: Not very strong and no Weapon Finesse, so her attack bonus and damage suffer. No SR.
Notable SLAs: None.
Final Evaluation: You have better rogue-analogues available to you. Malcanthet just doesn't live up to the same potential in combat as she does in tempting mortal souls.

Aspect of Orcus
CR: 9
HD: 9
How to get it: None by RAW, likely SM VIII
Role: Brute
Fluff: Orcus is the demon prince of the undead, twice dead and hence returned. He is bloated and corpulent, and loves to bide his time sitting on his massive throne. His aspects wield a lesser copy of the Wand of Orcus and are more willing to go out into the world. Orcus despises Graz'zt and Demogorgon, and devotes nearly all of his resources to their destruction.
Advantages: Decent damage with his wand. Critical hits threaten instant death.
Disadvantages: Slow and comparable to the broadside of a barn in combat - low AC. Poor attack bonus. No SR. Unholy weapons probably don't help you much (unless you're playing an evil game), and the instant death criticals only threaten 10% of the time, and it's a rather easy DC to beat.
Notable SLAs: None.
Final Evaluation: Fat, clumsy, and rather pointless. You have much better options in melee at this level, and none of them involve summoning the demonic version of Orson Welles.

Aspect of Pale Night
CR: 7
HD: 9
How to get it: None by RAW, likely SM VII
Role: Assassin
Fluff: Pale Night is rumored to be the mother of the entire tanar'ri race, including such major players such as Graz'zt. She is inscrutable but enjoys torturing eladrin in particular. Her aspects maintain her ethereal nature. She has no enemies among the demon lords, with all giving her a wide berth.
Advantages: Incorporeality and Spring Attack is an evil combination - you can pop out from solid objects to use her CHA-draining touch attacks. With her perfect fly speed, you can play hide and seek all combat long. Truth Beneath the Veil can leave your foes comatose and amnesic.
Disadvantages: CHA-drain can take a long time to disable foes. Truth Beneath the Veil is probably useless, as your enemies won't try to get a good look at her. But if they do, bam.
Notable SLAs: None.
Final Evaluation: A bit ponderous, but Pale Night can force your foes to play a deadly game of whack-a-mole. Given enough time and the right environment, she can infuriate plenty of enemies. She works best against foes with low CHA, obviously, so have her concentrate on uncouth warriors and stuck-up wizards.

Aspect of Pazuzu
CR: 8
HD: 9
How to get it: None by RAW, likely SM VIII
Role: Assassin/Manipulator
Fluff: Pazuzu rules the skies over the Abyss, and is the missing link between the obyrith and the tanar'ri. He commands the obedience of evil avians (a power his aspects share) and focuses his efforts on corrupting the innocent. Pazuzu has few enemies, though Graz'zt has been known to direct unkind words his way.
Advantages: A good fly speed. Four attacks a round with his greatsword and his talons. His aura makes evil flying creatures save or waste their attacks on him.
Disadvantages: Spring Attack, not Flyby Attack, which ends up being a very poor choice. He has a poor attack bonus. No SR.
Notable SLAs: None.
Final Evaluation: This one's a bit of a toss-up - if your DM allows a flying creature attacking Pazuzu to know about his aura and change targets before hand, eh. But if the creature doesn't, it wastes its action if it fails the save. That's pretty handy as a distraction against flying foes.

Aspect of Zuggtmoy
CR: 6
HD: 7
How to get it: None by RAW, likely SM VII
Role: Brute
Fluff: Zuggtmoy is the demon queen of fungi , spawning in her vast cesspools of vegetative matter. Her aspects maintain her abilities to engulf her foes. Zuggtmoy's greatest enemy is Juiblex, as they war constantly over the same layer of the Abyss.
Advantages: Her plant-based immunities are handy. Four attacks with good damage. She can grapple, constrict, and engulf foes.
Disadvantages: Like many of her demonic aspect compatriots, she has a number of grappling abilities but not the modifier to support them. Her attack bonus is low. No SR.
Notable SLAs: None.
Final Evaluation: Decidedly not a fan of this whole crappy grappler angle with the demon lord aspects. Zuggtmoy's the lowest among them, and as such just as useless, if not more so.

A quick note: Unlike most other aspects, the ones here HAVE spell resistance!

Aspect of Asmodeus
CR: 12
HD: 15
How to get it: None by RAW, likely SM IX
Role: Overlord
Fluff: Asmodeus, the Lord of Ninth, Master of Nessus, and no less than the King of Hell, is a very powerful foe indeed - perhaps one of the most dangerous in all the planes. His aspects are blessed with his mastery of hellfire, bedeviling magic, and melee might. They likely have better things to do than serve you (their creator has them on a tight leash), so they will require a good deal of convincing to join your side - not to mention that their use can draw the eye of the original.
Advantages: Certainly lives up to his reputation as the best option from this section - aspects of Asmodeus can really lay down some pain. Violate Spell-like Ability can be useful against pesky regenerating or healing foes - 10d8 irresistable damage (half of which is vile) is a good deal. They have great fly speeds and good defenses like high AC, SR, and Mirror Image. When they run out of spells they're still capable in melee. If bound, they can summon amnizus or Nessian warhounds.
Disadvantages: STR and CON are a a bit low, but the high HD total helps with that. Susceptible to electricity.
Notable SLAs: Chain Lightning, Hellfire Storm, Magic Circle Against Good, and Mirror Image 3/day, plus True Seeing 1/day.
Final Evaluation: Among your best blasters at this level. Hellfire Storm is great for bypassing fire resistance, so they'll always be viable. Though they'll run out of spells quickly, they can wade into melee and soak up a lot of attention. They've got it all: melee power, defense, mobility, and the capacity to cause some widespread devastation against your enemies. Highly recommended.

Aspect of Baalzebul
CR: 11
HD: 13
How to get it: None by RAW, likely SM IX
Role:
Fluff: Baalzebul, the sluglike Lord of the Seventh, occupies his current form as a punishment meted out by Asmodeus - he used to be tall and regal, a fallen angel. Ruling over Maladomini, he represents the sins of pride and ambition, constantly scheming to increase his prestige. His aspects retain his sluggish, disgusting appearance and his affinity for flies. Though intelligent and cunning, he's likely to be enticed by the promise of status and respect - his aspects even more so.
Advantages: Disgorge Insects is a decent little breath weapon, doing 15d6 in a 60' cone. He can also use those flies as a defense, gaining 20% concealment. He can burrow, though not quickly.
Disadvantages: Slow and slimy, with piddling slam attacks. Heavily dependent on the luck of the roll, as you can end up having to wait six rounds before spitting out flies again. AC's just shy of decent.
Notable SLAs: None.
Final Evaluation: A source of respectable area damage, as long as you don't use him against anything with Evasion. But that's about all he can do - unlike an aspect of Tiamat, he's useless in melee. I don't find that his breath weapon makes up for his shortcomings, so I can't recommend him highly, but those flies do hurt.

Aspect of Bel
CR: 9
HD: 11
How to get it: None by RAW, likely SM VIII
Role: Brute
Fluff: Bel is the Lord of the First and spends most of his time marshaling the forces of the Hells against the legions of chaos. Hiis aspects focus less on his tactical mind and more on his prowess with a sword. Fighting the tanar'ri is his main goal - point him in the direction of demons (legitimately or not) and he'll probably align himself with your cause. Beware, though - Bel is known for treachery.
Advantages: A fairly damaging combatant in melee with a flaming greatsword, Bel is also a halfway-decent grappler (at least, the abilities to back it up) and moderately mobile. Fairly high AC and HP for his level.
Disadvantages: For a purported melee fighter, Bel's a little lackluster - his STR is a little on the low side. Also, a disappointing grapple modifier makes him somewhat incapable at one of his supposed specialties.
Notable SLAs: None.
Final Evaluation: All in all, a capable high-level bruiser, though not the best you have available to you at this point - the Vrock still edges him out slightly in nearly all areas except raw damage. Still, throw on Power Attack and you might be able to cleave your way through mooks.

Aspect of Belial
CR: 10
HD: 12
How to get it: None by RAW, likely SM VIII
Role: Manipulator
Fluff: Belial is the deposed Lord of the Fourth, having nominally given power over to his own daughter, Fierna. Belial's aspects maintain his silver tongue and way with words, always ready with a quick retort or an insidious enchantment. Belial's quite the charming rogue, so beware his honeyed demeanor.
Advantages: His cursespewing ranseur can give a foe -4 to basically everything, a potent debuff. Does plenty of vile damage, so no healing for your foes. Decent HP and AC. A handy diplomat, too, in case you're lacking one.
Disadvantages: The will save DC on his cursespewing ranseur is easily beaten, leaving him with piddling damage. His DR is overcome by silver, not good, so probably more easily beaten by your foes.
Notable SLAs: Suggestion at will, plus Charm Monster 3/day.
Final Evaluation: Same problem as practically any other Enchantment-based summon: Mind Blank is available by now. Belial's a bit too much of a Hail Mary for my taste - his curses will rarely stick and his SLAs are easily immunized against. I'd pass.

Aspect of Dispater
CR: 10
HD: 13
How to get it: None by RAW, likely SM VIII
Role: Brute
Fluff: Paranoid, cautious, and an expert defender and fortifier, Lord of the Second Dispater rules over his the city of Dis with an iron (ha) grip. His aspects retain his power over metal and his expertise with his heavy mace, though their versions of the weapon pale in comparison to the original. You will have to overcome the aspect's distrust to even begin working out a deal - likely a tough negotiation.
Advantages: Rust is a decent option against armored foes, though the save DC is a bit lackluster (fortunately CON-based, so Augment Summoning will help). Relatively accurate in combat, too. They can also pitch in as a rogue or mechanical expert, with ranks in Appraise, Knowledge (architecture), Search, Open Lock, and Disable Device. He can at least summon a couple of bone devils (though only A.) as a bind and B.) with a 50% chance).
Disadvantages: Low damage makes Dispater less than compelling in a fight. Rust means you're destroying potential loot, which is always bad - and it's basically his signature ability.
Notable SLAs: None.
Final Evaluation: More useful out of combat than in it (though that's not saying much), Dispater's aspects face a lot of competition at this level. Rust might come in handy if you're barreling through a steel-clad dungeon or need to break into an armored airship, but in most situations I'd pass without a second thought.

Aspect of Fierna
CR: 9
HD: 12
How to get it: None by RAW, likely SM VIII
Role: Assassin
Fluff: The newly-appointed ruler of Phlegethos, Fierna is hedonistic and lustful to the core. Her aspects retain her fascination with flame and carnage. Less subtle than most archdukes of Hell, Fierna can be lured into combat for the mere possibility of wreaking havoc with her searing, scarring fire.
Advantages: She can be pretty handy with her Mortalbane Flameblade, tumbling through combat and landing searing blows. She's quick and mobile, with high AC and Spring Attack. She can also function in a limited artillery capacity with Fireball.
Disadvantages: Fire resistance shuts her down hard, as she's pathetic in melee otherwise - very low damage and unimpressive HP. Mortalbane can only be used five times a day - and it's unclear whether that means per casting or per hit (at least with Flameblade). I'm inclined to go per casting, making it more effective, but if your DM rules otherwise, she becomes less useful with her blazing blade.
Notable SLAs: Flame Blade at will, plus Dispel Magic, Fireball, and Fireshield 3/day.
Final Evaluation: If you're fighting a foe susceptible to fire, she's a decent, though not stellar choice. But seeing as how most of your enemies will have at least token resistance to fire, she's likely going to sit and rot in the corner of your summoning stable, undeserving of use.

Aspect of Glasya
CR: 11
HD: 13
How to get it: None by RAW, likely SM IX
Role: Assassin/Manipulator
Fluff: Daughter of Asmodeus, Glasya is the Lord of the Sixth, Malbolge. She is imperious and arrogant, believing heavily in her own superiority. Her aspects retain her aerial mobility and her befuddling, wisdom-sapping touch. In combat, she delights in tormenting enemies, so she might be lured into your service by such temptations.
Advantages: One of the few flying aspects, Glasya's wings and Flyby Attack feat serve her well - she can swoop down, drain some WIS, and soar back up out of reach. This tactic can also make her a useful debuffer for you, lowering the will save of your foe. Decent AC.
Disadvantages: Pitiful damage with her scourge, even if it is keen. Her summoning brings some lackluster bodies into the fray - kalabons pretty much suck by now, and an erinyes won't be making much of a difference. She's also relatively frail.
Notable SLAs: None.
Final Evaluation: Well, against a low-WIS foe, she can be a good choice. But her method of attack is a bit too protracted for me to heartily recommend her - she's a one-trick pony, and it's a trick that is easily quelled. When robbed of that, she has nothing to recommend her over other choices at this level.

Aspect of Kurtulmak
CR: 11
HD: 12
How to get it: None by RAW, likely SM IX
Role: Caster
Fluff: Kurtulmak, god of the kobolds, is conniving and without compassion - his only goal is the survival and domination of his chosen race, especially over gnomes. His aspects concentrate on the sorcerous power imbued in all kobolds by dragonsblood. Likely single-minded and humorless at the negotiating table.
Advantages: Hey, getting a 12th level caster is usually a good deal. Kurtulmak's spell choices here are pretty solidly blasty - but his summoning picks make him a good choice for a bind, as he can bring more meat shields into play. Polymorph, Greater Invisibility, and a good array of metamagic are all pluses too. He can also fight decently in a pinch, with good reach and damage.
Disadvantages: His DR is overcome by chaotic, so beware of using him against demons and other minions of entropy. His spells are easily defeated by elemental resistances, so choose your targets carefully.
Notable SLAs: None, but sorcerer spell picks include: Disintegrate, Lesser Dragon Ally, Summon Monster V, Greater Invisibility, Polymorph, Summon Monster IV, Dispel Magic, Fireball, Hailstones, Lightning Bolt, Alter Self, Melf's Acid Arrow, Scorching Ray, Magic Missile, Ray of Clumsiness, and Ray of Enfeeblement.
Final Evaluation: One of the few caster types that can still throw down in a scrap, an aspect of Kurtulmak is usually a pretty good choice. I'd prefer to bind one to make use of its summoning abilities (and to make him use his own gold and XP to call a dragon into my service), though that doesn't detract from its worth as a summon. A fine choice all around.

Aspect of Levistus
CR: 10
HD: 12
How to get it: None by RAW, likely SM VIII
Role: Assassin
Fluff: Levistus, Lord of the Fifth, rules from his prison deep within a glacier in the heart of Stygia. Though sophisticated and urbane, he is consumed with the desire for revenge against Asmodeus. His aspects retain his prowess with a rapier. He frequently plots with yugoloths and even demons, so his loyalty to the Hells is suspect - use that to your advantage in a mercenary bargain.
Advantages: I'm a fan of that Magebane rapier. Combined with his Precise Strike ability and his high critical chance, an aspect of Levistus can be a decent distraction against a mage (or anything with SLAs). With Elaborate Parry, he can also boast one of the highest ACs of your summons, making him a good decoy against dimwit bruisers. Very mobile, too, with Spring Attack and high ranks in Balance and Tumble.
Disadvantages: Against non-spellcasting, crit-immune critters, Levistus' aspects are incredibly weak.
Notable SLAs: None.
Final Evaluation: A situational summon, the aspect of Levistus is nevertheless a consummate duelist under the right circumstances. Obviously, he is best used as a caster killer, but you're going to have to do something about their defenses first. But then, as a caster yourself, that's practically your job anyway.

Aspect of Mammon
CR: 10
HD: 11
How to get it: None by RAW, likely SM VIII
Role: Brute
Fluff: The Lord of the Third, Mammon presides over primarily over wealth and greed. He is two-faced and deceitful, and will manipulate shamelessly to get what he wants - which is wealth, loyalty, and power. His aspects retain the musculature of his serpentine form, winding into combat to coil and crush their foes. He is a consummate traitor, and should be bargained with using the utmost of care.
Advantages: Aspects of Mammon have constricting abilities, and are passable in combat. Spring Attack lets him dart in and out of combat to harry your foes. Fairly durable, too, and can potentially summon bearded devils or narzugons.
Disadvantages: A grappler without the raw modifier to truly succeed at it, Mammon's far from overwhelming in melee. Low damage, low BAB, and few options to recommend it.
Notable SLAs: None.
Final Evaluation: Mammon's aspects are ironically not worth much at all. They won't scratch most creatures' DR at the time you can summon them, and their feat selection encourages mobility at the cost of raw power. They're ostensibly grapplers, but can't hack it. Skip them, skip them so hard.

Aspect of Mephistopheles
CR: 11
HD: 15
How to get it: None by RAW, likely SM IX
Role: Brute
Fluff: Mephistopheles, ruler of Cania and Lord of the Eighth, is a bitter, powerhungry devil, always looking for an angle to depose his master, Asmodeus. His aspects share his fascination with hellfire, a flame of his own invention, and can use that fire to sear even the most resistant foes. They are relatively urbane and comfortable in mortal society, and frequently work with mortal allies.
Advantages: With his flaming ranseur and his permanent hellfire shield, an aspect of Mephistopheles is decent in melee. His wings make him more mobile than many other aspects, and he is an excellent negotiator with high ranks in Bluff, Diplomacy, and Intimidate, as well as a smattering of obscure Knowledge skills. Immune to cold, too.
Disadvantages: Notably weak and frail - only 15 in STR and CON. Hellfire Burst is pretty much a non-ability - 2d6 with a save for half is crappy, even if it's impossible to resist.
Notable SLAs: None.
Final Evaluation: The aspect of Mephistopheles is meant for melee but is hardly good at it - while he can do a bit of damage with the ranseur, his physical stats are frighteningly low for a bruiser. Hellfire basically sucks too, and that's just about all he can do. An easy pass.

Aspect of Sekolah
CR: 13
HD: 18
How to get it: None by RAW, likely SM IX
Role: Brute/Caster
Fluff: God of the sahuagin, Sekolah is vicious, cruel, and unforgiving. His aspects retain the merciless power of his jaws and his spacious gullet. Sekolah is aloof and does not concern himself with even the concerns of his chosen, so dealing with him (without being devoured) might be difficult.
Advantages: Possessing a highly-damaging bite, the aspect of Sekolah is also very mobile (Swim-By Attack and Sahuagin Flip help out here), allowing him to dart in and out of combat, carrying death between his serrated teeth. If a group of foes needs some softening up, boom, Horrid Wilting. If you need to separate one from the pack, hey guess what, Swallow Whole, Improved Grab, and the grapple modifier to make it work. Fast and durable to boot.
Disadvantages: Aquatic-only and Gargantuan. Unholy Blight will see limited use in a non-evil campaign. AC is a touch on the low side, but Unholy Aura can boost it.
Notable SLAs: Horrid Wilting, Unholy Aura, and Unholy Blight 1/day.
Final Evaluation: Best. Aquatic. Summon. Ever. Think of it like a bigger, badder fiendish dire shark, only with a one-shot 18d6 cannon shell added on top. Seriously. Sekolah's that good. If you're underwater, he's your go-to guy. Err, shark.

Envoy of Lolth
CR: 12
HD: 10
How to get it: None by RAW, likely SM IX
Role: Manipulator/Caster
Fluff: This particular aspect of Lolth is focused on the seductive nature of the spider goddess. The Envoy is extremely charming, relying on her diplomatic abilities. Dealing with a goddess, even an aspect of one, is a difficult business, and you'll likely need to take extreme precautions.
Advantages: 10th level sorcerer casting, with a focus on enchantment spells and formidable DC's. Her aura gives all enemies a penalty to will saves, and does not offer a save itself. Good AC. Immune to enchantments. Fantastic social skills.
Disadvantages: Barely average in melee. Very limited elemental resistance and relatively low SR for her level.
Notable SLAs: None. But Sorcerer spells include Feeblemind, Charm Monster, Confusion, Fly, Heroism, Suggestion, Blur, Daze Monster, Tasha's Hideous Laughter, Touch of Idiocy, and Charm Person.
Final Evaluation: If you want a 10th level enchantment-based sorcerer on your side, then hey, Envoy of Lolth! I personally love the school, and the aspect's DC's are pretty good for the level, but you're still summoning an enchanter at a level when Mind Blank is not only in play, but ubiquitous. And again, you're dealing with the aspect of a goddess, specifically her trickery aspect. So, you know, watch your back.

Aspect of Graz'zt
CR: 11
HD: 16
How to get it: None by RAW, likely SM IX
Role: Brute/Manipulator
Fluff: Graz'zt is supremely seductive, a veritable obsidian Adonis. He is a formidable mage as well, though his aspects retain little of this ability, focusing instead upon Graz'zt's proficiency with a sword. He spends his time plotting and scheming, particularly against Orcus and Demogorgon.
Advantages: Great in melee with his greatsword, with a good bonus and formidable damage. He can seduce a foe into attacking its fellows as a swift action at a great DC. He also has an eldritch blast for a ranged option. Decent AC.
Disadvantages: Sanctuary aura is fairly useless, as you want your summons to be attacked. Size Alteration is a non-entity. Mind Blank, as always, shuts down his abilities. No SR.
Notable SLAs: None.
Final Evaluation: A good melee choice, though not quite as powerful as the abyssal giant. The addition of beguiling abilities is nice, but again, you're high level enough that mind-affecting abilities are easily negated.

Aspect of Obox-Ob
CR: 12
HD: 15
How to get it: None by RAW, likely SM IX
Role: Brute
Fluff: Obox-Ob, once the mighty prince of demons himself, has been pushed out of the spotlight in favor of the rising tanar'ri. A hideous amalgam of insect, arachnid, and decrepit shrunken head, his aspects retain his power over venom and vermin. He spends most of his time raging throughout his layer, plotting a return to power and the destruction of Demogorgon.
Advantages: Three decent attacks, Flyby Attack, and an INT-draining poison. He also releases swarms of demonwasps when damaged, making him three creatures for the price of one, though only when bound. Those swarms can potentially dominate and zombify your foes. Good AC and resistances. Constant True Seeing.
Disadvantages: His damage is disappointing. No SR.
Notable SLAs: None.
Final Evaluation: Not as good offensively as other summons at this level, Obox-Ob may be a good idea for his mobility and swarm-producing ability (again, only when bound though). I'm not a huge fan, but he could be a hell of a distraction.

Aspect of Yeenoghu
CR: 10
HD: 14
How to get it: None by RAW, likely SM VIII
Role: Brute
Fluff: Yeenoghu is the demon lord of gnolls, convinced of his race's superiority. He is savage and moves into combat with a triple flail. His aspects retain his melee might. Yeenoghu particularly despises Malcanthet and Baphomet, and wages war on both.
Advantages: Pretty savage in melee, with highly-damaging stunning flail strikes. Decent AC for his level.
Disadvantages: A fairly limited brute, with no tactical abilities or exceptional senses. No SR.
Notable SLAs: None.
Final Evaluation: Good in melee, crap at everything else. One of your better SM VIII bruisers, though.

Aspect of Hextor
CR: 11
HD: 12
How to get it: None by RAW, likely SM IX
Role: Brute
Fluff: Hextor is the god of conquest and war, rampaging over anything he can. Though far from stupid, he prefers to wade into battle with a savage glint in his eye. His aspects retain his prowess in combat and his multilimbed attacks. His greatest enemy is his half-brother, Heironeous.
Advantages: Eight attacks per round and nigh-unbreachable DR.
Disadvantages: Low DR, AC, and attack bonus. No SR.
Notable SLAs: None.
Final Evaluation: While he certainly has a good bit of damage potential, his attack bonus is low enough that he's going to rarely connect. Likely, Hextor won't live up to his reputation as the god of war.

Aspect of Lolth
CR: 11
HD: 14
How to get it: None by RAW, likely SM IX
Role: Assassin
Fluff: Lolth is the goddess of the drow, cruel and calculating. Her aspects maintain her arachnid nature and skills. Her greatest enemies are the gods of the elven pantheon, but she despises most other beings.
Advantages: A brutal STR-draining poison at a decent attack bonus. Plenty of strange, obscure skills. One of the few aspects with SR.
Disadvantages: Low damage and only one attack per round. Low AC and HP. Poison immunity makes her near-useless.
Notable SLAs: None.
Final Evaluation: The foes you're likely to want to use poison on are likely foes with good Fort saves. Given how easily poison is negated (and her lack of other options), I don't find this aspect of Lolth to be a good idea. Use the Envoy instead.

Aspect of Nerull
CR: 12
HD: 16
How to get it: None by RAW, likely SM IX
Role: Brute/Assassin
Fluff: Nerull, Greyhawk's god of death, is known as the Foe of All Good, as he represents malice in its purest form. He regularly consorts with fiends and the undead. His aspects reflect his mastery of negative energy and his ability to find his way through guarded places.
Advantages: Decent damage with his scythe, and a potential undead healing battery with Inflict Critical Wounds. He has a rather surprising complement of rogue skills, with Disable Device, Open Lock, Appraise, Search, and Craft (alchemy).
Disadvantages: Low AC and HP. No SR.
Notable SLAs: Inflict Critical Wounds at will.
Final Evaluation: You have better rogue options. You have better melee options. But you might not have better necrotic healing options (except perhaps the Oculus), so Nerull might be considered for that.

Aspect of Vecna
CR: 10
HD: 10
How to get it: None by RAW, likely SM VIII
Role: Caster
Fluff: Vecna, once an exceptionally powerful lich, is now the dark god of secrets and forbidden arcane lore. His aspects retain his skill with magic, albeit with a much more limited repertoire. Vecna's greatest enemy is his treacherous lieutenant Kas, though he has foes ranging from Iuz the Old to St. Cuthbert to the Lady of Pain.
Advantages: Very good scholarly skills. Undead immunities. Good against incorporeal foes with a ghost touch dagger and magic missile at will.
Disadvantages: Very low HP, due to his lack of a CON score. Exceptionally poor in melee.
Notable SLAs: Empowered Magic Missile, at will.
Final Evaluation: At the very least, Magic Missile is always a dependable option. But it does so little damage that summoning Vecna is like plinking away at a tank with an airsoft gun - sure, you might get lucky eventually, but you're going to need a lot more firepower to get the job done.

Aspect of Tiamat
CR: 13
HD: 12
How to get it: None by RAW, likely SM IX
Role: Caster/Brute
Fluff: The queen of evil dragons, Tiamat is greedy and destructive. She cares only about the rise of her children. Her aspects retain her multiheaded capabilities, breath weapons, and poisonous stinger. Her greatest enemy and direct opposite is Bahamut, the lord of all good dragons.
Advantages: Six damaging attacks per round with a painful CON-draining poison. Each of her five heads can breathe a 40' cone or line of varying elemental energy every 1d4 rounds, though only one head can do so in a given round. Great elemental resistances and attack options. Her AC is above average for her level. Blindsense 60'.
Disadvantages: Poor maneuverability. A good reflex save combined with elemental resistances or Evasion can shut her breath weapons down fairly easily.
Notable SLAs: None.
Final Evaluation: This version of Tiamat is much better than the Miniatures Handbook version, and it's also one of the best aspects you have available to you. You can use her as a mobile artillery platform, or have her deliver some severe pain in melee with her five bites. She's not the best melee summon you have, but she's in the top ten. The version in the FCII Web Enhancement is essentially the same, but trades damage for maneuverability. Not a fair trade in my mind - stick with this one.

Ethereal Defiler
CR: 16
HD: 22
How to get it: GPB with both Improved Calling and Infernal Bargainer, or Imbrue.
Role: Caster/Brute
Fluff: Strange, eldritch creatures from beyond the ethereal veil, Defilers exist almost solely to murder and destroy. They're instinctual, unthinking creatures, though they possess a rudimentary cunning.
Advantages: They have a eldritch blast-like ability a la the warlock, making them effective (if somewhat underwhelming) snipers. They can also imbue their claw attacks with the energy. When jumping into the Material, they do a fair bit of damage with their eldritch burst. They're capable in melee, shut down teleportation around them, and have a hefty HP total.
Disadvantages: Though they're quite brutish, they're not all that damaging. Their Tainted Energy blasts can only affect one attack per round (though as a swift action), making it somewhat inferior to other sources of d6's. Poor DR for their level.
Notable SLAs: None.
Final Evaluation: Man, it's like a warlock mini-Godzilla. For all the hoops you have to jump through to bind one, though, you're still better off with a Balor.

Spirrax
CR: 18
HD: 26
How to get it: Implore with Improved Calling and/or Infernal Bargainer
Role: Overlord
Fluff: These nautiloid wanderers roam the planes looking to destroy all life. They are inscrutable and alien, collected and calculating.
Advantages: A goodly number of decent tentacle attacks, plus CON drain upon grappling (and they're great grapplers). Void Blast is great - 30d6 damage in a burst or a long line. Stellar defenses and plenty of HP. A perfect fly speed and Flyby Attack. Blindsense 300', but only for living creatures. Very easily bound.
Disadvantages: Their shell can break, reducing their defenses significantly but giving them two more attacks. Their Indifference Aura is downright useless. Upon their death, they open up a random planar rift, which could really screw you.
Notable SLAs: Plane Shift (self only) at will.
Final Evaluation: Kind of a middling grab-bag, but potentially highly damaging with Void Blast. Only very specific builds are ever going to use one, though, and they're not so great as to warrant building towards their use.

Steelwing
CR: 14
HD: 15
How to get it: None by RAW, maybe SM IX
Role: Brute/Assassin
Fluff: These steely birds are native fauna in Acheron, guarding their eggs ferociously. A number of them have been trained as warbeasts and mounts. Though not evil, they are fierce and brook no theft from their nests nor the murder of their mates.
Advantages: Their razorfeathers are quite nasty - they augment the Steelwing's wing attacks, making them keen. They also do 5d6 damage to any creatures adjacent to the bird, while giving it concealment against all nonadjacent foes. They can also expel them as a 60' cone, doing 15d6 damage. It's all slashing, too, so not as easily resisted as elemental damage. They have DR 15/adamantine (not often bypassed), a great AC and formidable Fast Healing. Steelwings are also fast fliers and have five accurate attacks per round. Immune to cold.
Disadvantages: They're not evil, which screws them up for Malconvokers. Other than that, there's not a whole lot else to snipe at - Steelwings are solid choices. Their damage is a little lackluster, but all the razorfeathers whipping around make up for that.
Notable SLAs: None.
Final Evaluation: Like I said before, quite solid. So much so, in fact, that I'd consider them as a Malconvoker summon even though evil creatures are going to give me a better deal. Of course, as a bind, alignment isn't much of an issue. Really impressive damage potential and respectable defenses make the Steelwing a great choice.

Abrian
CR: 1
HD: 2
How to get it: None by RAW, likely SM II
Role: Minion
Fluff: Demonic ostriches. Seriously, how many demonic birds do you really need in an ecology? They roam in packs in the Abyss and other lower planes. Smarter than they look, but they're still fairly dumb.
Advantages: Augmented critical on their beak. Two atacks per round that do acceptable damage.
Disadvantages: Weapon Finesse is a wasted feat for them - Multiattack would be so much better. Relatively fragile.
Notable SLAs: None.
Final Evaluation: It's just not very good. But it's SM II. What did you expect?

Canomorph (harakin, shadurakal, and vultivor)
CR: 5, 11, 9
HD: 4, 10, 8
How to get it: None by RAW, likely SM V, SM IX, and SM VIII
Role: Brute/Assassin
Fluff: Cruel and intensely competitive, canomorphs are fiendish hounds that have learned how to assume human form to further their devious aims. None of them are particularly intelligent or charismatic, but they have a sly cunning. Slippery, shadowy, and untrustworthy.
Advantages: The vultivor has a decent sneak attack. The harakin can rage. The shadurakal wields a nasty spiked chain to good effect. For their other abilities, see the entries for their base creatures (Hell Hound, Shadow Mastiff, and Vorr, respectively).
Disadvantages:  They're heavily martial, so they don't scale well. No DR or SR makes them quite vulnerable.
Notable SLAs: None.
Final Evaluation: Mostly they're just low-level base classes jammed on top of an already-existing creature and called a "unique," which falls into the whole "Monsters with class levels" thing. If you need a low-level fighter, barbarian, or rogue, by all means. But you shouldn't really need one in the first place.

Chronotyryn
CR: 19
HD: 17
How to get it: GPB
Role: Overlord
Fluff: These strange, double-brained birds proclaim themselves to be the masters of time. They are said to be native to Acheron, though now far-flung across the planes. They are arrogant and selfish, but are not said to be particularly cruel or vicious. Likely, they'll be amenable to a mutually profitable deal.
Advantages: Two rounds per round. That's right, they can act twice on each turn. 12th level sorcerer casting (with great picks), great SLAs (including Time Stop!), and a host of metamagic feats, (Quicken, Maximize, Still, and Silent). They are a walking repository of knowledge. They have high resistance to every element, good DR, and daunting SR. Their AC is scary high.
Disadvantages: No good in combat, though you would probably have to be really dumb to try that.
Notable SLAs: Blink, Feeblemind, Greater Teleport at will, plus Displacement and Time Stop 3/day, plus Iron Body, Plane Shift, and Temporal Stasis 1/day. Sorcerer casting typically includes spells like Disintegrate, Cloudkill, Baleful Polymorph, Greater Invisibility, Black Tentacles, Slow, Sleet Storm, Fog Cloud, Obscuring Mist, and Grease.
Final Evaluation: Really, you should have been sold already with dual actions and spellcasting. But unlike most "typical lists," the Chronotyryn's isn't total crap. Instead of loading up on fireballs and lightning bolts (okay, they do know Lightning Bolt), they have a solid collection of useful spells focusing on battlefield control. A great spellcasting bind.

Darkweaver
CR: 10
HD: 9
How to get it: None by RAW, likely SM VIII
Role: Manipulator
Fluff: These arachnoid hunters from the Plane of Shadow made their way to the Material to find more suitable prey. They lie in ambush to sap the strength of foes, caring not for whom or what they devour.
Advantages: Shadow Strands can be effective battlefield control - it shuts down darkvision and blindsight, while forcing your foes to struggle to move any direction other than towards your summon. That's effective tanking power. They have all-around vision and cap sap strength with their bites.
Disadvantages: Awful in melee, their tentacles do terrible damage and their bite is at such a low attack bonus that it'll rarely connect. Their strands are somewhat easy to escape from and Freedom of Movement shuts them down completely.
Notable SLAs: Confusion, Suggestion, Darkness, Tongues, and Web 3/day, plus Shadow Walk 1/day.
Final Evaluation: I like the fact that they can shut down a wide area with their strands, though there are plenty of ways around their abilities. Shutting down blindsight is a rather unique ability, which might come in handy. But they're certainly not going to kill anything on their own - they work best as a screen.

Demodand (farastu, kelubar, and shator)
CR: 11, 13, 15
HD: 11, 13, 16
How to get it: Farastu is summonable by RAW at SM IX (though I'd shift it down to SM VIII), while the kelubar might qualify for SM IX and the shator must be bound by GPB.
Role: Brute, Assasin, Overlord
Fluff: Demodands are foul wardens and caretakers of prisons in Carceri. They are immense, preening, and enjoy bullying weaker creatures. They follow a rather strict hierarchy, however, and refuse to attack one another. They are cruel and domineering, though not savage, and despise serving others. Farastu and kelubar are likely used to being pushed around, while the shator may take a bit more persuasion.
Advantages: The Farastu is a semi-effective melee combatant while raging and is covered in a resinous tar that can disarm opponents and boosts their grapple modifier. The kelubar has sneak attack, damaging acidic slime on their claws, and a nauseating stench. The shator has 8th level sorcerer casting, permanent Mind Blank, and a paralyzing spittle. All Demodands have permanent Freedom of Movement and a complement of SLAs.
Disadvantages: None of them are very impressive in melee, being neither particularly strong nor blessed with vast reserves of hit points. Few of their SLAs end up being useful.
Notable SLAs: All of them have the following: Detect Magic, Clairaudience/Clairvoyence, Fear, Tongues, and Invisibility at will, plus Fog Cloud and Ray of Enfeeblement 2/day, plus Dispel Magic 1/day. Kelubars add Acid Arrow and Spider Climb at will, plus Acid Fog 2/day. Shators add Spider Climb at will, plus Cloudkill and Stinking Cloud 3/day, plus Mass Charm Monster 1/day. Shators' sorcerer casting typically includes spells like Confusion, Fireball, Blink, Hideous Laughter, True Strike, and Enlarge Person.
Final Evaluation: I'm not impressed with their SLAs, nor am I impressed with them in combat. They have a goodly number of cloud and fog spells, but if you're a conjurer (which you should be), you probably do them better. The demodands are middling choices, outdone by your much better options.

Ethergaunt (black, red, and white)
CR: 17, 9, 13
HD: 16, 5, 11
How to get it: None by RAW; GPB, SM VIII, and SM IX
Role: Caster
Fluff: If the stories are to be believed, ethergaunts were once inhabitants of the Material who left for the ranges of the Ethereal Plane. They are now extremely advanced and alien, scoffing at things like religious devotion and emotion. They see mortals as insects to be casually swatted - you'll likely have to prove your importance or intelligence in order to become more than a nuisance in their eyes. Perhaps you could offer one a unique specimen as fodder for their experiments.
Advantages: They all cast as wizards with a level equal to their CR and can become completely immune to all spells under a certain level. They can open their masks to reveal their hideous alien features, draining the mental stats of all those around them. They can also Dominate creatures 3/day and keep them as thralls.
Disadvantages: They can only remain on the Material Plane for one round per HD, after which they require an hour of recharge before they can manifest again. That is a serious problem with binds, though less so with summons. They're also fairly fragile, with low HP totals and no DR. None of them can stand up to anything in melee combat.
Notable SLAs: None, but they all have wizard casting. Typically, they memorize spells like Enervation, Bigby's Crushing Hand, Horrid Wilting, Sunburst, Finger of Death, Prismatic Spray, Project Image, Greater Dispel Magic, Mass Suggestion, Disintegrate, Wall of Force, Feeblemind, Mind Fog, Cone of Cold, Resilient Sphere, Greater Invisibility, Haste, Vampiric Touch, and Glitterdust, plus others.
Final Evaluation: The black ethergaunt might be the best spellcaster available to you. Though the Chronotyryn has an edge with dual actions, the ethergaunt can cast 9th level spells. Reds and whites are useful too, and summonable. Essentially, you're summoning a 9th or 13th level wizard - and that's always a good idea. Add on their unique abilities, and you've got a summon I would normally highly recommend - but that "Can only affect the Material for one round / HD every hour" gives me pause. Most combats won't last that long, but keep it in mind.

Gathra
CR: 10
HD: 9
How to get it: None by RAW, likely SM VIII
Role: Brute
Fluff: These boar-like brutes are are fiendish predators on the blasted fields of Avernus in the Hells, chasing down and devouring any prey they can catch.
Advantages: Decent tanks with reserves of HP and hefty DR.
Disadvantages: They don't do enough damage for my tastes. Most things will save against Bellow at this level. Trample is never a great idea. Very poor reflexes.
Notable SLAs: None.
Final Evaluation: Do you really need a brute at SM VIII? Even if you do, you can easily find something more effective than the Gathra. Skip them.

Kaorti
CR: 1
HD: 2
How to get it: SM II
Role: Caster
Fluff: Once-mortal wizards who pushed into the Far Realm, Kaorti are now a twisted race of their own, mutated and malformed. They exist solely to transform living creatures into their thralls and bring about the rise of the Far Realm. They are alien at best and insane at worst, so deal carefully with them.
Advantages: They have a small selection of SLAs, which is very nice at this low of a level. Color Spray and Ray of Enfeeblement give you some action economy in the debuffing and control arenas. Their kaorti resin weapons have a x4 critical multiplier (not that you'll send them into melee often). They have decent AC, too. Possible cheese alert: they can transform other creatures into kaorti (though it requires eight hours, so this trick is bind-only), giving them -4 STR, +4 INT, +4 WIS, and +6 CHA amongst other things. You turn neutral evil (not necessarily a bad thing for some) and "embrace the kaorti racial ethos". Plus you gotta wear a resin suit.
Disadvantages: Weak, not very healthy, and awful in most forms of combat. Not all of their spells are that useful.
Notable SLAs: Alter Self, Color Spray, Feather Fall, Ray of Enfeeblement, Spider Climb, and Reduce Person 1/day.
Final Evaluation: For one spell, you get three to six others. That's a pretty good deal, though not all of them are supremely useful. Casters are quite rare at this level, so the kaorti is a fine choice when you need some magical backup. Once their spells are depleted, have them Alter Self into a combat form and go to town - it's the best of both worlds.

Khaasta
CR: 3
HD: 3
How to get it: None by RAW, likely SM III
Role: Minion
Fluff: Savage lizard people who dwell in the Outlands, pillaging and plundering. They are quick to betray any potential employers and masters, so watch out.
Advantages: Not bad in melee with a halberd. They can also throw down with a composite longbow, if you need some ranged support.
Disadvantages: No special abilities - these guys are just brutes, and not great ones.
Notable SLAs: None.
Final Evaluation: Blah. Not impressed. Though they're mechanically sound, they lack any sort of cool abilities and are really just another body to throw into the mix. Run-of-the-mill.

Phiuhl
CR: 11
HD: 9
How to get it: None by RAW, likely SM IX
Role: Manipulator
Fluff: Phiuhls are vengeful spirits of slain elementals that haunt the plains of the Gray Wastes. They exist only to spread misery and death. There seems to be no reasoning with them.
Advantages: They can drain CON with their gaseous forms, or drain levels with their dessication aura. Enemies attempting to charm them are in for a Feeblemind surprise.
Disadvantages: Low AC and middling HP for their level. Their fire damage is pitiful.
Notable SLAs: None.
Final Evaluation: While they make good debuffing clouds, they just don't do enough real damage to be worth it. They can cripple spellcasters, however, and if you're looking to manufacture a Wightocalypse scenario, they'd be the right choice.

Planetouched (maeluth and wispling)
CR: 1/2, 1/2
HD: 1, 1
How to get it: None by RAW, likely SM I
Role: Minion
Fluff: Maeluths and wisplings are tieflings of the dwarven and halfling worlds. Treat them as you would any other planetouched race.
Advantages: Maeluth get +4 CON. Wisplings gain a bit of INT over normal halflings.
Disadvantages: Maeluths suffer from a DEX penalty rather than a CHA penalty, which makes them lesser warriors. Fiend Hammer won't help you very much, unless you're going to face good foes.
Notable SLAs: None.
Final Evaluation: See comments on other races for proper uses - I'll give you a hint, it involves class levels. Wisplings might be useful for their Small size, while Maeluths are somewhat hardier than a normal tiefling.

Slasrath
CR: 7
HD: 8
How to get it: None by RAW, likely SM VII
Role: Brute
Fluff: These flying worms roam Gehenna and the Gray Wastes and often serve as yugoloth mounts. They are of animal intelligence, so likely require no bargaining.
Advantages: Their poison can damage all physical stats. Their Wing Slash attack can feasibly damage a large number of foes on a charge, and does respectable damage. Perfect fly speed.
Disadvantages: No resistances of any kind and low AC. Their fly speed is somewhat slow. Not actually evil.
Notable SLAs: None.
Final Evaluation: Not bad for a flying mount, though other choices are faster and hardier.

Steel Predator
CR: 13
HD: 12
How to get it: None by RAW, likely SM IX
Role: Brute/Assassin
Fluff: Metal-eating cat-like predators on Acheron, Steel Predators aren't evil but are driven by hunger and the desire to consume iron. Offer them your foes' metal items - assuming that you don't want to loot them first.
Advantages: Three attacks a round at a respectable bonus with Pounce and Rake make them okay combatants, and their Sundering Bite is good when you really want to deal with a troublesome weapon or piece of armor. They have blindsight and can emit a damaging sonic roar. Significant DR and AC. Quite stealthy.
Disadvantages: Subpar damage means you're going to have to chip away at your opponents. You won't be able to order without telepathy or Terran writing, as it is quite deaf. Like the Slasrath, not evil.
Notable SLAs: None.
Final Evaluation: Not quite as good in melee as the Jarilith, the Steel Predator is still useful when you really need to sunder something. Keep them in reserve for those few times when biting a sword in half is going to count.

Terlen
CR: 2
HD: 4
How to get it: None by RAW, likely SM III
Role: Brute
Fluff: Flying. Sharks. All you need to know.
Advantages: Quite mobile in the air, on land, or in water. They do double damage against flat-footed opponents. Decent AC.
Disadvantages: For giant flying sharks, they sure don't do much damage with their bites. Poor HP. No resistances. A poor grapple modifier makes their Improved Grab somewhat less-than-inspiring.
Notable SLAs: None.
Final Evaluation: Well, they are low level which may redeem them somewhat. But they're unimpressive damage-wise, at least compared to the fiendish ape and the celestial bison.

Varrangoin (arcanist, lesser, and rager)
CR: 11, 6, 8
HD: 8, 5, 10
How to get it: None by RAW, likely SM IX, VI, and VII
Role: Caster, Minion, and Brute
Fluff: These gargoyle-like creatures are denizens of the Abyss, though they have been pushed out of their natural habitat by the tanar'ri. Essentially, they are demonic bat people, gathering in flocks to harass and devour others. They are cruel and not easily controlled.
Advantages: Arcanists can cast as level 9 wizards and are immune to low-level spells. Ragers and Lessers have breath weapons and poisonous stingers, though Ragers are the only ones likely to use melee to decent effect with four attacks and Rend. They also can take an extra standard or move action, which mostly just means they attack again. They can all fly, at least.
Disadvantages: They're all fairly fragile, with low CON, low AC, and poor resistances other than their breath weapon's energy type.
Notable SLAs: Ragers can use Dispel Magic and Fear 2/day. Arcanists typically memorize spells like Cone of Cold, Ice Storm, Vampiric Touch, Fireball, and Flaming Sphere.
Final Evaluation: The wizards are blasters and the fighters are fairly ineffective, chipping away with plinking little claws and teeth. They're just don't cut it.

Vorr
CR: 4
HD: 3
How to get it: None by RAW, likely SM IV
Role: Assassin
Fluff: Again with the doggies. Vorrs are cruel canines that roam the Abyss, lurking in shadows and ambushing unsuspecting prey. Treat them with a pack mentality and you just might convince them to follow you.
Advantages: Three attacks per round with 2d6 sneak attack and free trip attempts. Shadow Form gives them a healthy array of resistances and immunities.
Disadvantages: No resistances outside of Shadow Form. Low attack bonus and damage. Not very hardy.
Notable SLAs: None.
Final Evaluation: Better than the Hell Hound, I think. Precision damage is uncommon at this level, so it can be nice. But the real question is this: can it stand up to the Voor? No? Thought not. Shadow Form is nice, though, making it essentially untouchable for the duration of the summon.

Phantasmal Slayer
CR: 15
HD: 16
How to get it: GPB
Role: Caster/Manipulator
Fluff: These creatures are literally fear incarnate. Their motives are indiscernable beyond their desire to spread terror - capitalize on that and let it spread fear amongst your enemies.
Advantages: They can cause an automatic Phantasmal Killer effect at a formidable DC, though they have to hit with their incorporeal touch attacks first. They can overcome all non-metal-based DR. Perfect fly speed, high AC, and incorporeal traits.
Disadvantages: Immunity to fear shuts them down cold.
Notable SLAs: Scare at will, plus Crushing Despair, Fear, and Ray of Exhaustion 3/day, plus Feeblemind and Waves of Fatigue 1/day.
Final Evaluation: If you like scaring the crap out of your foes, hey, bingo. It's reasonably tenacious in a fight, though it's not gonna do a whole lot of damage. But they can act as a debuffer and if your foe is susceptible to fear, they're gonna be in for a rough ride.

Marruspawn Abomination
CR: 19
HD: 20
How to get it: GPB
Role: Overlord
Fluff: Formed out of ill-advised experiments combining spawn magic and godsblood, this abomination is said to be responsible for the downfall of an entire civilization. It is wrath and malevolence given form. It might serve you if you offer it release from its prison, though it's likely to angry about going from one imprisonment to another.
Advantages: Extremely damaging. It can turn all those around it into salt as a free action every few rounds. Great SLAs, plenty of DR and HP. Quite possible the highest AC in this entire guide. Blindsight and phenomenal Fast Healing. It can summon gargantuan fiendish monstrous scorpions. An army in a can!
Disadvantages: Nothing, really. A difficult bind, with +32 Sense Motive and 25 CHA.
Notable SLAs: Parching Touch and True Seeing at will, plus Flesh to Salt, Sandform, and Summon Monster IX 3/day, plus Symbol of Thirst 1/day.
Final Evaluation: These guys are whirling cyclones of death and devastation. They ended entire civilizations. What have you done recently? Comparable to the Balor in my mind - and with slightly lower CHA as well. Go for it.

Draegloth
CR: 5
HD: 6
How to get it: None by Raw, likely SM V
Role: Brute
Fluff: Deformed demonic half-breeds between drow and demonic servants of Lolth, Draegloth are favored servants of drow houses and matriarchs. They are vicious and cunning, and binding them might incur the wrath of at least minor drow, not to mention bigger players up to Lolth herself.
Advantages: Decent enough damage (on par with the Bar-lgura) in melee, and a few handy options between their SLAs and their necklace of fireballs, type II.
Disadvantages: Poor AC. Fairly fragile. Not that much better than just having summoned a drow, and who wants to do that?
Notable SLAs: Darkness 4/day, plus Desecrate, Faerie Fire, Unholy Blight, and Dancing Lights 1/day.
Final Evaluation: A big fat eh. Unimpressive, though they can throw down a few decent fireballs as limited artillery. Their options are limited and they're not overwhelmingly good at any one of them.

Earth Whisper
CR: 5
HD: 4
How to get it: None by RAW, likely SM V
Role: Manipulator/Caster
Fluff: The Earth Whisper is a malevolent spirit from the Elemental Plane of Earth. They love to lure miners to their doom, whether by inspiring greedy infighting in them or by a petrifying touch. They especially despise those that plunder the depths of the earth. Perhaps you can offer to return some treasure to the earth to appease them.
Advantages: They can turn comrades against each other with their Avarice ability, as many enemies you will face will have material wealth of some kind. Cavern Fear can cause foes to try to climb down steep pits and chasms, and if they have poor ranks in the skill, you might be able to eliminate them (but only underground). Their touch attacks drain DEX and can eventually petrify foes.
Disadvantages: Hardly a contender in a fight. Not much HP.
Notable SLAs: Stone Shape at will, plus Spike Stones and Wall of Stone 3/day.
Final Evaluation: Interesting abilities, but limited utility. They shine in caverns and subterranen complexes, though, and stone-manipulating SLAs are always welcome in the world of Dungeons and Dragons.

Kython (broodling, juvenile, adult, impaler, slaymaster, slaughterking)
CR: 1, 3, 5, 8, 11, 13
HD: 2, 6, 10, 12, 15, 18
How to get it: None by RAW, likely SM II, SM IV, SM V, SM VII, SM VIII, and SM IX
Role: Brute
Fluff: The offspring of long-dead fiends trapped on the Material Plane, the kythons have only their race's survival in mind. They are cruel, merciless, and thrill to rend other creatures to shreds. Give them the chance to tear others apart and they may consent to your service.
Advantages: They all do respectable damage with a STR-draining poison. They have great AC and decent HP. Impalers make great chargers, while Slaymasters are decent grapplers. Slaughterkings are beastly in combat. Both Slaymasters and Slaughterkings can emit auras that debuff non-kythons and improve their own defenses. They all have blindsight, elemental resistances, and their own strange mutated weaponry. Kython weapons offer such beauties as entangling mucus, grappling mouth sphincters (I kid you not), and free action incorporeality.
Disadvantages: No DR. None of them are very mobile.
Notable SLAs: None.
Final Evaluation: They're all viable choices in melee, and they scale well with a kython for nearly every occasion. I love the Disruption Field, as it doesn't offer a save and really messes up your enemies. Kythons are great picks, especially the higher level ones.

Vaath
CR: 4
HD: 6
How to get it: None by RAW, likely SM V
Role:
Fluff: Vaath hail from Carceri and are sadistic and malicious as they come. They live to torture foes not just physically, but mentally as well - letting them wallow in fear as they see their impending doom from its burrowing claws.
Advantages: Their DEX-draining poison does the job fairly well, and when they reduce a foe's DEX to zero, they can burrow inside it and kill it instantly. They also cause WIS drain to all those viewing the burrowing. Decent AC.
Disadvantages: Their bite attack is at a fairly low bonus, so they're rarely going to get the chance to actually burrow. Relatively low HP.
Notable SLAs: None.
Final Evaluation: Totally creepy. While their ability has the potential to be killer, you're going to have jump through some serious hoops to get it to work. Eh. Too much work for the benefit - skip 'em.

Abyssal Drake
CR: 9
HD: 10
How to get it: None by RAW, likely SM VIII
Role: Brute
Fluff: The product of a horrible demonic breeding program designed to create flying mounts for demon princes and lords, Abyssal Drake proved too wild and unruly to tame for ridership. Now they are simply wild predators in the vast reaches of the Abyss. Dumb but willful, they can probably be convinced to serve you simply for prey.
Advantages: A Huge flyer, which makes them an excellent potential mount. You might even be able to fit four people on it, if you go by the squaring sizing rules. It has a nice breath weapon, 10d6 fire (half of which is divine) and a halfway decent poison attack with its stinger. Flyby Attack makes it a mobile harrier, diving in and rending with its claws. An extremely fast flyer.
Disadvantages: By the level you get it, its Frightful Presence is useful. Awful aerial maneuverability. Physical damage is lackluster at this point. No DR, either.
Notable SLAs: None.
Final Evaluation: I like the Abyssal Drake because it's one hell of an intimidating mount. If you need to get somewhere fast (and can't teleport for some reason), they're not a bad bind. They're not the heaviest hitters, but they're great skirmishers and transportation.

Shadow Beast (ghirrash, khumat, and thaskor)
CR: 7, 8, 9
HD: 7, 11, 13
How to get it: None by RAW, likely SM VI, VII, and VIII
Role: Brute
Fluff: Mercenary creatures from the Plane of Shadow, Shadow Beasts are ruthless yet loyal to their evil masters. Though animalistic, they're surprisingly intelligent and should not be underestimated based on their appearance.
Advantages: The ghirrash has five attacks per round, pounce, and two rake attacks. It also has a permanent 50% displacement effect on it. Khumats are capable grapplers with a powerful bite attack and plenty of natural armor. They're also fairly stealthy and great swimmers. The thaskor is decently damaging with high AC and a stunning blast. It's also rather oddly diplomatic, with good ranks in Bluff, Diplomacy, and Intimidate. They all have decent elemental resistances and a high attack bonus.
Disadvantages: They all have easily-bypassed DR (except the thaskor). The ghirrash doesn't do enough damage, and the khumat and thaskor only have one attack per round.
Notable SLAs: None.
Final Evaluation: They can be capable brutes in combat, but they're really only going to be doing one thing: attacking, over and over again. If you're looking for a bruiser, yeah, by all means. I don't like the ghirrash too much as it won't often overcome DR. The khumat is only mediocre, though is good in aquatic situations. The thaskor, however, is a decent pick.

Genie, dao
CR: 7
HD: 8
How to get it: None by RAW, likely SM VII
Role: Caster
Fluff: Dao are earth genies, primarily spending their time in their lavishly decorated cities on the Plane of Earth. Though not cruel or sadistic, they are arrogant and consider other creatures as chattel or resources to be thrown away once consumed.
Advantages: Their SLAs are at a CL of 19, with decent choices. They also have high Appraise and Craft scores, in case you need an emergency jeweler.
Disadvantages: Just two attacks, at a middling bonus. Low AC, no DR or SR.
Notable SLAs: Alter Self, Detect Magic, Gaseous Form, Invisibility, Misdirection, Passwall, Persistent Image, Wall of Stone at will, plus Move Earth and Transmute Rock to Mud 3/day.
Final Evaluation: See comments on the efreeti for the Wish thing - they shouldn't be allowed, end of story. Dao can be decent controllers with their stone walls and mud pits, while they can let you bypass dangerous dungeon corridors with Passwall. Just don't use them as bruisers - they won't suffice.

Frost Dwarf
CR: 1
HD: 1
How to get it: None by RAW, likely SM II
Role: Minion
Fluff: Frost dwarves are the descendants of a tribe of duergar abducted and forced to serve Kostchtchie and his frost giants in the Abyss. They are cruel and domineering, but desire revenge and freedom more than anything else - perhaps a little white lie about opposing their masters' goals might convince them.
Advantages: Like standard dwarves, but with more CON and less CHA. They're a little stealthier than most dwarves, and have a couple of SLAs.
Disadvantages: They have light sensitivity.
Notable SLAs: Obscuring Mist and Chill Touch 1/day.
Final Evaluation: More class level potential. Plenty of CON is nice on a summon, and the CHA penalties just make them easier to manipulate and deceive.

Nightmare, lesser
CR: 4
HD: 6
How to get it: SM IV (replacing either fiendish dire wolf or howler)
Role: Brute
Fluff: It's like a nightmare, but lesser! Seriously. They're just not as good at plane-hopping.
Advantages: Exactly the same as the nightmare, but one CR lower.
Disadvantages: Exactly the same as the nightmare, but without Astral Projection or Etherealness.
Notable SLAs: None.
Final Evaluation: Considering that their stats are almost exactly the same, and that lesser nightmares lose the abilities that make nightmares phenomenal summons/mounts, there's no way you should ever go for the lesser version. I prefer both the wolf and the howler.

Pack fiend
CR: 8
HD: 8
How to get it: SM VII (replacing Huge fiendish monstrous scorpion)
Role: Brute/Assassin
Fluff: Pack fiends were once hunting hounds of both devils and demons, though now they have mostly thrown off the yoke of service and roam free among the Gray Wastes, preying on any unlucky souls they can find.
Advantages: Three decent attacks per round with Pounce. They also have a STR-draining poison. Blindsight's always nice, and they can make decent trackers.
Disadvantages: Only so-so HP and damage.
Notable SLAs: None.
Final Evaluation: Falling somewhere between a bruiser and a stealthy skirmisher and yet somehow excelling at neither, the Pack Fiend is nothing special. Replacing the scorpion is a decent idea (as it sucks), however, but you can replace it at the same level with better choices.

Shadow Eft
CR: 5
HD: 6
How to get it: None by RAW, likely SM V
Role: Assassin/Brute
Fluff: Drawn from the Plane of Shadow to areas touched by psychic trauma, shadow efts have no qualm about harvesting mental energy from other sentient creatures - they feel that it is their place to be the predators. Convince them you serve the "Unmerciful Void" - their strange shadow god.
Advantages: They can be effective melee combatants between their decent damage, Spring Attack, Lion's Charge, and Truevenom. Quite stealthy, especially in darkness. Shadow Body can make them quite evasive and mobile.
Disadvantages: Not especially hardy. Avoid daylight at all costs.
Notable PLAs: Duodimensional Claw, Truevenom, and Psionic Lion's Charge 3/day, plus Shadow Body 1/day.
Final Evaluation: Not a bad deal at all. They're available relatively low, do decent damage, and can stay alive when things get tough. I like 'em.

Souleater
CR: 7
HD: 8
How to get it: SM VII as an evil caster (replacing Huge fiendish monstrous scorpion)
Role: Brute/Manipulator
Fluff: Souleaters are horrific beasts that roam the Gray Wastes, feeding off soul energy. They'll likely only serve you if you offer them souls - a rather dubious moral endeavor.
Advantages: They emit a level-draining aura and consume the souls of the fallen to strengthen themselves. Decent damage and three attacks.
Disadvantages: Low AC, no DR, and no SR make them relatively vulnerable. They're vulnerable to turning.
Notable SLAs: None.
Final Evaluation: Their draining aura and consumption of souls don't discriminate between friend or foe, making them a risky proposition. Not a great pick, but could act as a walking debuff against casters or incarnum users.

Arcanoloth
CR: 17
HD: 12
How to get it: PB
Role: Caster
Fluff: Arcanoloths are scribes and archivists for the Yugoloths, and are scheming, triple-dealing fiends always looking for an angle in every situation. However, they are noted for being generally honorable and true to their word - at least as far as you can trust a fiend's words. Careful, specific language and commands are recommended.
Advantages: They cast as a 12th level sorcerer, though they have no specific spell-list listed. Immune to mind-affecting spells and a decent complement of SLAs. Good social and academic skills, plus they can read or write any language. Decent fly speed.
Disadvantages: Notably fragile, with only 11 CON. In fact, keep them as far away from the fray as possible, since they're basically completely inept. Their poison is crappy.
Notable SLAs: Fly, Heat Metal, Invisibility (self only), Magic Missile, Warp Wood, and Shapechange (!!!) at will, plus Fear and Major Image 1/day. Plus sorcerer casting.
Final Evaluation: These guys are all about the spells. That's a hefty HD/CR split, and should make you seriously consider them as option for a bind. However, their fragility is a major drawback - most enemies can just look funny at them and they'll keel over. Of course, that's what Shapechange is for. Likely straight-up broken.

Marraenoloth
CR: 10
HD: 10
How to get it: None by RAW, likely SM VIII
Role: Caster
Fluff: Marraenoloths are the archetypical boatmen of the Styx, skeletal creatures who ply the oily waters with their skiffs. They frequently arrange ambushes of their passengers, and they dislike leaving the comfort of their ferries. A quick return to their craft is probably the best incentive you can offer.
Advantages: Very little - halfway decent SLAs. Somewhat speedy.
Disadvantages: Fragile, awful in melee, and lacking in options outside of their SLAs, which aren't phenomenal to begin with.
Notable SLAs: Alter Self, Animate Dead, Charm Person, Phantasmal Killer, Poison, and Produce Flame at will.
Final Evaluation: Well, if you're really hurting for a ferry captain to cross some river (and have no other options, which seems unlikely), you might summon one. Mostly they're forgettable. You have so many better options at this point that the Marraenoloth shouldn't even cross your mind.

Yagnoloth
CR: 10
HD: 10
How to get it: None by RAW, likely SM VIII
Role: Brute
Fluff: Possessed of one massive, damaging arm, Yagnoloths are feudal lords and minor tyrants of their realms, though they are despised by nearly every other Yugoloth for their status. They are hulking and brutish, but not dumb or socially inept. Perhaps a small respite from their constant paranoia might be a welcome change of pace.
Advantages: A formidable save DC on their stunning blow makes them halfway decent in melee, though only halfway. Much more durable than their peers in the Yugoloth hierarchy.
Disadvantages: Their weapon-wielding arm is powerful weak, with a crappy attack bonus and pathetic damage. Their breath weapon does 2d6 damage and only affects a 5' cone, which is basically awful. Their only SLA is a pitiful one.
Notable SLAs: Shocking Grasp 3/day.
Final Evaluation: While they're better than the Marraenoloth (though only by virtue of their stunning arm), the Yagnoloth still sucks royally. Don't even think about it. Move on. Nothing to see here.

Canoloth
CR: 5
HD: 6
How to get it: None by RAW, likely SM V
Role: Brute
Fluff: Canoloths are dog-like skirmishers and scouts in Yugoloth armies, often having been demoted to the position as punishment for some long-forgotten transgression. They are barely intelligent, preferring to rely on their brutish dispositions and wicked barbed tongues. An easy fiend to manipulate.
Advantages: Pretty beefy. As I've mentioned quite often, I'm a big fan of summons with Blindsight. Their tongue attack is at a decent bonus, can reach out to 20', and can paralyze foes for three to eight minutes on a failed save, the DC of which is respectable. Fairly quick and agile, too. Being immune to sight-based attacks can come in handy if you're going up against a basilisk or a pesky gnome illusionist.
Disadvantages: Not much in the way of other options. Their SLAs have abominable DCs. Their grapple modifier, though not abysmal, isn't great. Their damage is merely okay in comparison to others of their level.
Notable SLAs: Detect Magic, Desecrate, and Cause Fear at will.
Final Evaluation: It's got 20' reach and a paralyzing tongue attack - that's a lot to love right there. Used well, the Canoloth can shut down weak-Fort threats and cause some general havoc on the battlefield. They're not your best damage dealers, but they can disable opponents with ease, leaving them helpless against future assault. Another prime candidate for throwing into a fog or a cloud spell (can you tell I love this tactic yet?).

Mezzoloth
CR: 6
HD: 10
How to get it: None by RAW, likely SM VI
Role: Brute
Fluff: Common foot soldiers, Mezzoloths are far from sophisticated, knowing only endless martial drills and the occasional productive torture session. They're pretty dim and likely prime candidates for fast-talk and complicated, labyrinthine contracts that put them at a disadvantage.
Advantages: Respectable melee combatants, the Mezzoloth also has the advantage of being able to throw down Cloudkills as a softener before rushing in. They also have a hefty HD total for their CR, which makes them a bit more durable than some summons (but also indicates that they're relatively weaker). Surprisingly decent stealth for a bruiser.
Disadvantages: They have no real way of seeing in their own clouds, which diminishes their advantage somewhat.
Notable SLAs: Cause Fear, Produce Flame, See Invisiblity at will, plus Cloudkill and Dispel Magic 2/day.
Final Evaluation: Fairly middling in terms of melee, with subpar casting and nothing much to recommend them. I'd go with a Kyton or an Excruciarch or, hell, a fiendish rhinoceros over the Mezzoloth any day.

Nycaloth
CR: 10
HD: 14
How to get it: None by RAW, likely SM VIII
Role: Brute
Fluff: Aerial skirmishers and flying cavalry, the Nycaloth holds a respected position in the Yugoloth hierarchy. They are savage when enjoined in battle, but prefer to remain distant and observe their foes from the skies until they are needed. They only have average intelligence, however, and tricking them into service shouldn't be too difficult.
Advantages: A hefty attack schedule with either a damaging greataxe or wounding claw strikes. If you ever feel like dropping foes from a great height, they have a quick flight speed and can climb to a point where they can do some damage.
Disadvantages: A relatively useless and sadly limited amount of abilities outside melee.
Notable SLAs: Fear, Invisibility, Mirror Image, and See Invisibility at will.
Final Evaluation: Though they're better than the Vrock in a straight-up scrap, they don't have a lot of options outside pure damage. Eh... better options at this point. Just middling.

Ultroloth
CR: 13
HD: 18
How to get it: None by RAW, likely SM IX (though the Ultroloth is notoriously under-valued in the CR department; I'd change it to at least a 16) or GPB
Role: Caster
Fluff: Ultroloths are scheming tacticians and crafty generals of the Yugoloth forces, the Ultroloths are devious, cunning, and notably lazy. They prefer to coerce their minions into doing their dirty work. They're expert bluffers and manipulators, though not to the extent of a Pit Fiend or a Balor.
Advantages: Great SLAs with a high caster level, Ultroloths can beguile and befuddle their foes while blasting away with all sorts of damaging and debilitating rays. Phenomenal magery, really. Plus, a Hypnotic Gaze, though it likely won't see use with all your other options.
Disadvantages: Pretty damn awful in melee, though why you'd put them in that situation in the first place is beyond me. Tricky binds, too.
Notable SLAs: Gaseous Form, Prying Eyes, Alter Self, Fear, Wall of Fire, Scorching Ray, Ray of Enfeeblement, Ray of Exhaustion, Scrying, See Invisibility, and Suggestion at will, plus Binding, Geas, Enervation, and Mass Suggestion 3/day, plus Symbol of Death 1/day.
Final Evaluation: No DM in his right mind should give you these guys as a summon - they're way too good as magical artillery. Whether its debuffing, control, or straight up blasting you want, the Ultroloth has options to spare. I personally like mixing them in with Devils and using Wall of Fire to create chokepoints - but your foes' fire resistance is likely pretty high at this point. Do keep in mind, too, that like the Balor and the Pit Fiend, Ultroloths are aces in their respective hierarchies, and likely won't tolerate the yoke for long. Revenge comes swiftly to those who offend them.

Corruptor of Fate
CR: 5
HD: 7
How to get it: SM VI
Role: Assassin
Fluff: Corruptors of Fate are mercenary and opportunistic, selling their services to the highest bidder. They are quite happy to serve and in fact prefer to have a patron - they're also noted for not being terribly picky about whom they serve, though they nominally prefer evil lords. Should be an easy sell - just offer them the chance to spread suffering amongst your enemies.
Advantages: Corruptors are super-debuffers, with a cursing attack (leaves the enemy 50% likely to just do nothing), a debuffing gaze, and a permanent unluck effect when others try to damage them. They're also immune to necromantic effects and negative energy, making them helpful in concert with undead or other necromantic strategies.
Disadvantages: Underwhelming in melee, Corruptors aren't likely to do a lot of damage. Weapon Finesse always makes me sad - for a summoner with Augment Summoning, it's often a wasted feat for the fiend.
Notable SLAs: None.
Final Evaluation: While you may not want to summon hordes of them to crawl all over your enemies, a well-placed Corruptor can do wonders to surgically cripple major threats with their curse. Anything with a poor Will save is likely to be fair game - brutes and assassins beware. If you can get a cursed foe to concentrate on the Corruptor itself, even better - if they do get to act, they'll always be taking the worst of two rolls anyway. A fine choice for twisting destiny to your advantage.

Voor (normal and Dreadful Lasher)
CR: 4, 9
HD: 5, 15
How to get it: SM IV, SM VIII
Role: Brute
Fluff: Nasty, vicious, and dull, the wannabe xenomorph Voors are bred as guardians, like hideous daemonic rottweilers. They are only capable of comprehending simple commands, but they follow orders given by stronger creatures without question. They are willing to wait quite a long time to spread slaughter and havoc - perhaps you will afford them that opportunity.
Advantages: Six attacks a round at a more than respectable bonus for their level, the Voor is a veritable spinning murder top in melee. 20' reach with their tentacles (30' for the Lasher), Combat Reflexes and they can Rend if they hit with both of their claw attacks. Decent grapple score, too - +38 for the Lasher!
Disadvantages: Blindsense, not Blindsight, which just pulls the rug out from underneath fog-based tactics (sooo disappointing). Strict readings of RAW also give it a 50% miss chance, as it cannot actually see its foes. Middling AC and HP. Who really cares if they give off no natural scent, either?
Notable SLAs: None.
Final Evaluation: Love the voor. Love it. It has so much damage potential. It makes even blasting wizards look wimpy in comparison - two of them in tandem can just tear things apart. Hell, even one of them is a serious menace. If you can convince your DM to let you summon the Dreadful Lasher variety later definitely take that one too, as it's one of the best melee combatants at that power level - bigger, badder, and more full of tentacled, spiky death for your enemies. The voor is a great melee choice - probably one of the best. Unless, of course, it has a 50% miss chance on all its attacks, in which case, it becomes significantly less useful - even so, it's still worth summoning.

Piscoloth
CR: 9
HD: 9
How to get it: SM VII
Role: Minion
Fluff: Piscoloths are drill sergeants and minor troop commanders in Yugoloth armies - they are minor thugs and enforcers, thriving on what little authority they're given. Despite their imperious nature, they're quite stupid and easily manipulated.
Advantages: Eleven attacks a round is nice, though only three of them do any damage - the other eight can only paralyze. Hit enough times and something will eventually fail a save - it's a DC of 18, which isn't great but isn't awful, either. Decent SLAs. All-around vision might come in handy.
Disadvantages: Pathetic attack bonus for their level means that the paralyzing tentacles will rarely hit, making their utility less than paramount. Oddly slow in the water.
Notable SLAs: Blink, Fear, Scare, and See Invisibility at will, plus Meld Into Stone, Stinking Cloud, and Phantasmal Killer 3/day.
Final Evaluation: I could see them being used for ambush tactics in dungeons and caves with their stone-melding abilities. If you consider their CR to be accurate (which I do not), they're a decent deal for SM VII, though far from spectacular. If you're looking to capture your quarry rather than kill them, they'd be a good choice - but that's about it.

Skereloth
CR: 3
HD: 4
How to get it: SM IV
Role: Minion
Fluff: These wretched, twisted creatures are the lowest of the low in Yugoloth armies - they are cowardly and sniveling, used only for the easiest of infiltration and scouting duties. They'll bend like twigs to your commands.
Advantages: Four attacks per round plus sneak attack seems like it'd be decent. Fairly high AC and a burrow speed, plus high stealth skills.
Disadvantages: Middling attack bonus and pathetic damage, even with four attacks per round. Their Cringe ability just tricks an opponent into thinking that they're not worth the time and effort to kill - but you want opponents concentrating on your summons, not others.
Notable SLAs: Daze and Jump at will, plus Burning Hands and Expeditious Retreat 3/day.
Final Evaluation: "Other yugoloths regard Skereloths as weak and useless." You should too. Pitiful in combat, and you have much better scouting options available to you at this level. Pass.

Echinoloth
CR: 8
HD: 8
How to get it: SM VIII
Role: Minion
Fluff: Rear guards of advancing Yugoloths, Echinoloths are often assigned mop-up duty due to their relentless nature and vast love of shredding things to tiny bits. They're too dim to know when they're in a losing proposition - they'll likely succumb to your wiles.
Advantages: Tremorsense...? Rend and Infernal Wound... might add up? Nawww. Seriously, Echinoloths suck.
Disadvantages: Awful melee abilities for their level. Their Nauseating Aura has a woeful DC. Low AC and DR means they're chewed up like nothing at this point.
Notable SLAs: None.
Final Evaluation: Reality check: the Voor (which fills the exact same niche) has a slightly lower attack bonus, more attacks, and does roughly the same damage for a spell four levels lower. That alone should make you cringe at the prospect of ever summoning an Echinoloth. If you really need a tentacle beast at this level, use the Dreadful Lasher version of the Voor - same CR, so much better.

Battleloth (arrow, axe, crossbow, pick, spiked chain, and sword; Issue #306)
CR: 1, 2, 2, 2, 3, 3
HD: 1, 3, 4, 2, 3, 3
How to get it: None by RAW, likely SM II, SM III, SM III, SM III, SM IV, and SM IV
Role: Minion
Fluff: These foul, mischievous creatures were created for a war long gone, and now act as mercenaries. They are literal tools for their masters - they all can take the form of certain weapons. They are sly and manipulative, but fairly weak and likely easily commanded.
Advantages: The Arrow Battleloth has a very fast fly speed with perfect maneuverability at a very low level, making it a good aerial scout. The Crossbow 'loth is okay in weapon form, as it confers Precise Shot and reloads itself. It also can act as a rogue replacement with ranks in Disable Device and Open Lock. They all have DR at a very low level, which can come in handy. They can also function as low-level magic weapons, though you have better spells for that.
Disadvantages: They're all fairly weak in combat and quite fragile, even for their level. The Axe and Pick 'loths are especially useless.
Notable SLAs: None.
Final Evaluation: Only the Arrow and Crossbow 'loths are useful at all, and really then only at extremely low levels. They don't pass the bar in combat, so skip 'em.

Barbed
CR: 11
HD: 12
How to get it: SM IX
Role: Brute
Fluff: The Hamatula is a bodyguard and treasure guardian for the devils, loyally and fearlessly defending their charges. Hamatula are cruel and sadistic, but follow their orders explicitly (like most devils).
Advantages: They do plenty of damage with their grapple and barbs. Decent SLAs, with a good amount of variety. Somewhat stealthy.
Disadvantages: Relatively poor damage and attack bonus. Only two attacks? Sad. For a supposed grappler, too, they have an abysmal grapple modifier. Scorching Rays don't cut it at this point, either, especially when they can only fire two rays.
Notable SLAs: Scorching Ray, Major Image, and Hold Person at will, plus Order's Wrath and Unholy Blight 1/day.
Final Evaluation: Bah. I don't think Hamatulas are at all competitive for SM IX. Poor in melee, poor as casters. A serious disappointment, really.

Bearded
CR: 5
HD: 6
How to get it: SM V
Role: Brute
Fluff: Barbazu are shock troops and infantry legionnaires in infernal armies. In downtime, they serve as guards and sentries - they're loyal and committed to their duty, which they carry out with frenzied ferocity. Aggressive and eager to join battle, they're easily deceived to your side.
Advantages: Between your Augment Summoning feat, Deceptive Summons, and their Frenzy, they're excellent melee combatants. Their wounding glaives are handy against many foes. Low Sense Motives make them easy to deceive.
Disadvantages: Actually, very little - Barbazu are quite good at what they do, but serve little to no purpose in a non-combat situation.
Notable SLAs: None.
Final Evaluation: Thumbs up! They're not completely devastating in melee (at this level, fiendish giant crocodiles are the gold standard), but their intelligence makes them much easier to use tactically. You know exactly what you're getting with one, but what you're getting is a hell of a bruiser.

Bone
CR: 9
HD: 10
How to get it: SM VII
Role: Overlord
Fluff: Osyluths are the secret police and informers of the infernal world. They maintain extensive records on the activities of other devils for potential blackmail and extortion. They hate all other creatures and don't hesitate to bring their full wrath to bear. Harder to trick than some, but offer them to chance to destroy hated enemies of the Hells, real or imagined.
Advantages: Ooof! A CR 9 creature at SM VII? Nice deal. A decent attack schedule with a debilitating poison. A wide array of skills and SLAs, plus a Fear aura. A lot to love here.
Disadvantages: Little to none to speak of. Their melee damage isn't great for this level.
Notable SLAs: Dimensional Anchor, Wall of Ice, Major Image, Fly, and Invisibility, all at will.
Final Evaluation: No reservations here. A great bargain for the level, and a very effective combatant. While they're capable in melee, they really shine when using their SLAs for tactical control. Wall of Ice is particularly useful - divide and conquer. A good choice even if it was a level higher - as is, it's fantastic.

Chain
CR: 6
HD: 8
How to get it: SM VI
Role: Brute
Fluff: Kytons are devilish torturers, specializing in the torment and punishment of living souls. They are surprisingly human-like, much more so than most other fiends. They are wrapped in chains and have their own city in the Hells, called the Jangling Hiter. Not especially intelligent, and they love to cause pain, so should be an easy bargaining process.
Advantages: Oh, Dancing Chains. You make me happy. Four attacks a round, reasonably devastating. Kytons are fine melee combatants, but Dancing Chains makes them superb. Just remember, you have to supply the chains yourself. Also, Kytons have a nonexistent Sense Motive. Immune to cold,. Also Craft (blacksmith) at +17, just in case you have to give some metalwork a cursory glance for some bizarre reason.
Disadvantages: If you don't bring those chains, kytons drop in usefulness by quite a bit. Really kind of one-hit wonders. I really wish they had Combat Reflexes or Improved Trip.
Notable SLAs: None.
Final Evaluation: Not the most damaging melee choice around, their chains nonetheless give you reach and control over a battlefield. A bit one-dimensional, but still a good idea overall.

Erinyes
CR: 8
HD: 9
How to get it: None by RAW, likely SM VII
Role: Assassin
Fluff: Erinyes are the remnants of angels who fell, retaining their basic form but in a foul reversal. They are infernal succubi, basically, the concubines, scouts, and ranged combatants of the Hells. Slightly more charming than most devils, but they're expendable and often vulnerable in the hellish hierarchy, so a chance to get out of Dodge for a few days might appeal to them.
Advantages: A decent fly speed combined with their flaming composite longbows makes them effective ranged combatants, as they can flit above the fray and pick off enemies with ease. Their Entangle ability might find use if you want to drop an enemy from a great height. Permanent True Seeing. I also fully support any creature with Charm Monster at will!
Disadvantages: If they get stuck in melee, they're nowhere near as effective. Very few SLAs, though the ones they get are useful.
Notable SLAs: Charm Monster, Minor Image, and Unholy Blight at will.
Final Evaluation: As I've mentioned with the Arrow Demon, ranged combatants are rare in the SM line, so anything you can get is not a bad idea - but the Arrow Demon is also strictly better at its job than the Erinyes, with four more attacks a round with higher damage. But the Erinyes has mobility and flight, which may be more tempting to you.

Hellcat
CR: 7
HD: 8
How to get it: SM VIII
Role: Brute/Assassin
Fluff: Naturally invisible, bezekira enjoy lying in ambush to either tear mortals apart or convince them to do evil deeds - they enjoy playing games of wits, which may be their saving grace when you summon them. Riddles and philosophical discussions with the invisible fiendish lion? Why not?
Advantages: Natural invisibility's about it. Scouting duty, perhaps?
Disadvantages: Terrible melee attack bonus and damage for a supposed melee creature. Awful grapple, low HP. Not at all a competitive summon.
Notable SLAs: None.
Final Evaluation: First things first: boo on the SM/CR split here - SM VIII gets you a CR 7 creature? That's crap. Why use this when the fiendish dire tiger at the same level is better in practically every way? Pass, pass, pass.

Horned
CR: 15
HD: 16
How to get it: GPB
Role: Overlord
Fluff: Cornugons are elite forces in infernal armies and lordly retinues, standing tall and powerful. They tower over other devils, and instill even the hardiest denizen of the Hells with terror and grudging respect. They rarely retreat from a battle, preferring to whirl their spiked chains around to cause as much devastation as possible. Lure them in with the promise of unholy frenzy and limb-rending opportunities.
Advantages: Their spiked chains make them excellent controllers, given that they have a respectable attack bonus and can stun with every hit (DC 29 to negate!). They can quite literally tear things apart in melee, both your opponents and their weapons with their wounding tails and Improved Sunder. A diverse array of skills, a handful of SLAs and a fear aura make it multipurpose, too.
Disadvantages: Not very mobile, though they can fly. Their SLAs fall into two categories, mainly: various anti-good and anti-chaos spells, which you won't find all that useful, and blasting spells, which is good for you since you banned Evocation (or, at least, you should have), but they're not great spells to begin with. The fear aura has a limited radius. Formidable Sense Motive and CHA scores.
Notable SLAs: Persistent Image at will, plus Fireball and Lightning Bolt 3/day.
Final Evaluation: Unholy reavers in melee, horned devils are nevertheless somewhat poor outside of their milieu, though they can create a rather respectable fireworks show. But they're just one HD over Planar Binding, which makes me curse and rue them, as by them time you can bind them, you might also be able to grab a Balor or a Molydeus instead.

Ice
CR: 13
HD: 14
How to get it: None by RAW, likely SM IX
Role: Overlord
Fluff: Gelugons are a breed apart amongst devils, refusing to associate with other devils beyond strict command structure - they have one distinct role in the infernal hierarchy, and they serve it with relentless loyalty and almost no deviation. They are commanders of legions and troops of lesser devils, but are capable of summoning a feral bloodlust for battle when needed or found alone. Likely to chafe under your control.
Advantages: Fantastic summons, first off. Wicked melee damage, plus the numbing cold from their attacks slows your foes. 10' reach and Combat Reflexes. They make excellent controllers and blasters with their ice spells, and can project a nasty fear aura. They get any three knowledge skills, too, so shore up a few weaknesses in your book-learning. Durable, quick, and just plain nasty.
Disadvantages: Against foes with cold resistance, they quickly become much less useful in the blasting department. Not much else - Gelugons have few chinks in their chitinous armor.
Notable SLAs: Cone of Cold, Ice Storm, and Wall of Ice at will!
Final Evaluation: One of the very few summons that might make me consider spending a level nine spell, the Gelugon can give you rounds and rounds of divisive control, debilitating melee, and tactical flexibility. I prefer to bind them, as I enjoy them enough to want to keep them around longer.

Imp
CR: 2
HD: 3
How to get it: None by RAW, likely SM III
Role: Minion/Assassin
Fluff: Like quasits, imps are tiny fiendish creatures usually used as familiars by unscrupulous wizards. On their home plane, they are messengers, spies and schemers, abused by most everything above them in the Hells' chain of command. Notoriously fawning and servile - just show them how much more powerful you are than them.
Advantages: Good stealth and mobility as well as decent ranks in other skills. A DEX-draining poison, Fast Healing, and an alternate form ability make it a better combatant than it looks, but not by much.
Disadvantages: Weak damage, even in their alternate forms. Clearly not a combat choice.
Notable SLAs: Detect Magic, Detect Invisibility at will, Suggestion 1/day.
Final Evaluation: Good familiars, but not great summons. Poor in combat, but useful in more subtle ways. Not as good when they're only around for a round/CL.

Lemure
CR: 1
HD: 2
How to get it: SM II
Role: Minion
Fluff: Lemures are mindless shells, the forms that evil mortal souls take on when they first arrive in the Hells. They have no capacity for communication or control, only possessing a primal desire to tear anything they encounter apart. No need to bargain - just command.
Advantages: Decent low-level tanks with their DR.
Disadvantages: Just about everything here - they're mindless, hard to control, not at all damaging, and have no abilities. But then, this is SM II - what did you expect?
Notable SLAs: None.
Final Evaluation: Well, if you're really in the mood to have a lump of agonized flesh hanging around to mob your enemies and maybe take a few hits for you, by all means. But they're not going to be doing anything else.

Pit Fiend
CR: 20
HD: 18
How to get it: GPB
Role: Overlord
Fluff: Pit fiends are the infernal elite, second only to the Dukes and Princes of Hell. They are true paragons of evil power, being both cunning, strong, and influential. A Pit Fiend is a difficult creature to bind into service - not only will they likely resist your efforts, but they will make you pay dearly for the audacity. Tread carefully.
Advantages: Just straight-up brutal in melee, with a disease-inducing bite that also includes a poison with the secondary effect of death. They're also excellent casters, having a wide variety of abilities that let you carpet bomb your enemies or go at them with a bit more guile.
Disadvantages: Just as difficult to bind as a Balor, but poorer selection in the casting department. Wish is problematic - any DM worth his salt either won't let you use it (oh, this Pit Fiend already used his yearly allowance) or he will twist your Wish so hard the room will spin. Don't get cheesy - just don't use Wish.
Notable SLAs: Create Undead, Fireball, Mass Hold Monster, Persistent Image, and Power Word Stun at will, plus Meteor Swarm 1/day.
Final Evaluation: What's not to love here? Like most of the upper-level binds, the Pit Fiend will basically just mess up everything around you. Still, I prefer the Balor because they have slightly better SLAs. But the Pit Fiend is nothing to sneer at - they're just as capable in melee, and they can just kill you with their festering bites.

Advespa
CR: 3
HD: 4
How to get it: None by RAW, likely SM IV
Role: Assassin
Fluff: Advespas are flying scouts in the Hells, confining themselves strictly to their hierarchies. They can assume pleasing female humanoid shapes, and often do so to entrap mortals. Nevertheless, they're not exceptionally bright or sly, and can easily be duped.
Advantages: A large flyer with four attacks on a full attack and Flyby Attack is a great deal for the level. They also have a decent poison and some niche SLA picks. Regeneration, high HP, and DR also make them rather durable.
Disadvantages: Actually, not a whole lot - the advespa has a lot going for it. Low skills, I suppose.
Notable SLAs: Alter Self, Pyrotechnics, Produce Flame, and Command 3/day.
Final Evaluation: I quite like them - they're powerful, mobile melee combatants and they have enough SLA options available to them to be effective in other ways. Even without their other abilities, I'd summon them just for their combat prowess. A stellar choice.

Marrash
CR: 5
HD: 7
How to get it: None by RAW, likely SM V
Role: Assassin
Fluff: Marrashi are winged gnoll-like creatures from the Hells that thrive on spreading disease and filth. They attempt to not only kill their summoners, but to turn them into more marrashi with their taklif arrows. Beware!
Advantages: An excellent fly speed and decent ranged attack make them good with hit-and-run tactics.
Disadvantages: Disease is not how you want to deal with your enemies, and the marrash does rather disappointing damage with its attacks, so they're not likely to end up killing anything.
Notable SLAs: Protection from Arrows at will.
Final Evaluation: They're mobile, and that's about it. They won't be heavy hitters, nor do they have the artillery powers of an Erinyes or an Arrow Demon. Give them a pass.

Gulthir
CR: 6
HD: 6
How to get it: SM VI
Role: Manipulator
Fluff: Gulthirs are at once police and punishment in the hellish hierarchy. Higher devils are transformed (painfully) into gulthirs when they displease their masters, and so most gulthirs are desperate to regain their favor. They, in turn, can inflict torment on other devils by devouring and digesting them. Their loyal nature may make them an easy fiend to enslave.
Advantages: A rather interesting Swallow Whole ability - when facing evil outsiders, they can be digested, adding temporary HP and save bonuses to the gulthir. Against all others, it's a Dominate Monster with no initial save, though such minions are granted save attempts on subsequent rounds. Plus, you can't cut your way out of its gizzard, as no matter what as soon as you're swallowed, you're a mental slave. SLAs that complement its main ability - lower STR means a lower grapple!
Disadvantages: Given that you want to grapple foes with the Gulthir, they have a rather low grapple score. They only get one attack a round, though the one's really all you need if your foe is next on the menu.
Notable SLAs: Ray of Enfeeblement and Scare 5/day.
Final Evaluation: Interesting, at least tactically, the gulthir is a great tool against other evil outsiders, and a potentially encounter-turning Dominate factory (albeit a slimy one). I like them, but they're a rather specialized tool. Their HD total makes them ideal LPBs, though.

Remmanon
CR: 15
HD: 18
How to get it: GPB
Role: Manipulator
Fluff: The exceptionally arrogant Remmanon thrive on sowing discord and doubt amongst mortals, particularly enjoying tempting them into acts of jealousy and greed. They enjoy feigning servitude, even offering contracts when not bound by a magic circle. Likely to betray you at the first possible opportunity, or trick you into signing away your soul. Beware.
Advantages: The Insidious Aura is nice - it confuses only your opponents, and you get bonuses to hit the affected creatures. They could be a party taxi with Plane Shift.
Disadvantages: That's basically all the Remmanon has going for it - a rather pathetic array of options at this level. Pathetic damage and one attack a round. They have a fly speed, but it's quite slow.
Notable SLAs: Mostly teleportation abilities, though you do get Disguise Self.
Final Evaluation: No. Just no. A GPB should not be wasted upon a walking Confusion aura. It should be used upon unholy terrors like a Balor or a Pit Fiend. Not some scheming emo with a pretentious attitude and missing genitalia. It's not that they're total crap, it's just that compared to your other options, they're about as attractive as a filthy Honey Bucket baking in the desert heat.

Stitched Devil
CR: 9
HD: 8
How to get it: None by RAW, likely SM VIII
Role: Brute
Fluff: These twisted, misshapen forms are stitched together by night hags out of the carcasses of fallen devils. Their lives are pure pain, and they inflict this agony upon others. But they don't quite know whom to blame for their torment, and you can twist that ignorance to your confusion. Promises of relief, mercy, or even affection (though feel free to make them as empty as you like) will make them fawn over you, like hideous hellish lapdogs.
Advantages: Five attacks a round with a pain aura that causes an extra d6 of damage from any and all sources make them effective at helping your party rack up some damage. Helpful, if limited, SLAs. Oddly enough, decent trackers too.
Disadvantages: Neither their attacks nor their aura is particularly damaging, making them work well only with multiple iterative attacks or a host of individual sources. Not much to do outside of hacking away in melee, either.
Notable SLAs: Phantasmal Killer and Dispel Magic 1/day.
Final Evaluation: I don't find them to be very helpful, as you have much better melee options available to you at this point. Sure, the pain aura can certainly add up over time, but so can a Rogue's sneak attack, and people still crap all over the class. And like the Rogue, the Stitched Devils should be avoided at all costs and replaced with a more effective choice. Like a Vrock. Or a Factotum.

Abishai (white, black, green, blue, and red)
CR: 4, 5, 6, 7, 8
HD: 4, 5, 6, 7, 8
How to get it: Lawful evil caster required for all: SM IV (replaces fiendish giant wasp); SM V (replaces bearded devil); SM VI (replaces chain devil); SM VII (replaces bone devil); and none by RAW, but likely SM VIII (likely replacing hellcat)
Role: Overlord
Fluff: Abishai are gargoyle-like devils ferociously loyal to their divine creator, Tiamat. They are arrogant and love to trick and cajole mortals into contracts that lead them to eternal torment and suffering at their own hands. Claiming to serve Tiamat's interests or that of powerful chromatic dragons may make them your willing pawns.
Advantages: Hooray, Wrack! Four out of five have it, and it's basically a save-or-lose - the target is disabled for 1 round/CL. Abishai have plenty of options available to them - they're decent in melee with four attacks and an assortment of elemental damage, are mobile and durable, and come with some helpful magic items.
Disadvantages: They do suffer from a lack of definition, not being particularly effective in any one arena. They don't do tons of damage, nor are they particular quick or blessed with HP.
Notable SLAs: The actual abilities and uses differ from Abishai to Abishai, but mostly include Charm Person, Suggestion, Scare, Charm Monster, and Wrack.
Final Evaluation: A good option in many situations, Abishai are almost worth it for Wrack alone. Other summons do their jobs better, but few of them can match the Abishai for versatility.

Amnizu
CR: 7
HD: 9
How to get it: SM VI as a LE caster (replaces xill)
Role: Caster
Fluff: Amnizu are consummate bureaucrats and the guardians of portals and gates in the Hells. They are vile and hedonistic, but also relentless in their duty and quite cunning. They do have massive egos, however, and are easily flattered - pander to their inflated sense of self worth, and they might deign to "serve" you. They do resent taking orders, though, and often seek revenge.
Advantages: Quickened fireballs? A stupefying touch? Delightful! Amnizu can roast your foes like few other summons can, and are deliciously effective with their Int drain. Low-INT enemies can be drained into a coma almost instantly, while classes that depend on the stat will suffer immensely from the loss. Regeneration, too.
Disadvantages: Somewhat fragile, and their artillery quickly runs out. Fireball is a somewhat less-than-stellar spell and the save DC is a bit low, but it's free.
Notable SLAs: Quickened Fireball 3/day.
Final Evaluation: Hands down, one of my favorite summons. I shouldn't even have to go into detail as to why - the amnizu is a mobile artillery platform that remains very useful even after its ammunition is depleted. A level six spell that nets you a grand total of 60d6 fire damage (albeit across three rounds), and can drain your enemies' intellects dry is a spell worth keeping around.

Assassin Devil
CR: 11
HD: 14
How to get it: None by RAW, likely SM IX
Role: Assassin (duh)
Fluff: Gee, would you believe that they're assassins? No, seriously. When a devil needs something dead and it can't be caught doing the deed itself, they hire the Dogai. They're used against mortals most often, however, infiltrating societies and seeking out threats to the Hells both realized and potential. They are independent outcasts, however, and some may chafe against the ordered nature of their home. Use that to your advantage.
Advantages: You'll never see one coming - they can gain greater invisibility (as a swift action, but only for one round each time) or partial concealment at will, plus they have Fog Cloud as an SLA with 60' Blindsight. Phenomenal stealth and mobility, plus three good attacks with 5d6 sneak attack damage each. Spring Attack, to boot.
Disadvantages: High Sense Motive. Devilishly susceptible to non-visual detection methods - blindsight, mindsight, etc., shut down their stealth pretty hardcore. Damage is a little lacking, though sneak attacks make up for that.
Notable SLAs: Fog Cloud, Nondetection, and Tongues at will - Dimension Door if you bind.
Final Evaluation: Killer ninja. While the Kelvezu has higher sneak attack damage and more attacks, the assassin devil has a better attack bonus and blindsight. A beautiful choice in conjunction with fog and cloud spells, as they're just as effective while your foes are crippled and vulnerable unless they have blindsight too (though let’s be honest, by this level everything you face should have a way around that). More reliable in combat than your other rogue-likes, but likely the one with the least potential at this level. Kelvezus are capable of much more damage, and the Naztharune has better rogueish abilities.

Ayperobos Swarm
CR: 12
HD: 13
How to get it: None by RAW, likely SM IX
Role: Manipulator
Fluff: These tiny devils form locust-like swarms in the Hells and love to devour and rend flesh whenever they come across anything weaker than them. They especially despise other devils. Quite used to being downtrodden and therefore likely easily bound.
Advantages: Their Control Body is an interesting ability - they get to possess a distracted creature until they make a save to expel them. They can be effective controllers, sowing mayhem on the battlefiend.
Disadvantages: Unlike the Broodswarm, Ayperobos do not have Evasion and have low HP, making them very vulnerable to area attacks. They do very little damage, too, and disease is a terrible method of harming a foe. It's somewhat unclear whether or not their Control Body ability can affect multiple creatures at once.
Notable SLAs: None.
Final Evaluation: I don't think a swarm is going to cut it at this level. They might find use in distracting spellcasters, but they're mostly weak and far from your best option.

Harvester Devil
CR: 7
HD: 9
How to get it: None by RAW, likely SM VII
Role: Manipulator
Fluff: The scheming, soul-buying devils of Faustian legend, Falxugon are cunning, intelligent, and thrive on deceiving and seducing mortals. They disdain combat, only joining the fray when all other options are closed to them. Learn to B.S. a B.S.-er.
Advantages: Their Infernal Debt and Refuge of the Damned abilities can make for an interesting debuffer, one who taunts foes mercilessly until they try and attack it, and then stabs them with their lethargy-inducing blades. Falxugons also have excellent social skills (though surprisingly not much Sense Motive), letting them act as negotiators and infiltrators for you.
Disadvantages: They're weak, they do pitiful damage, and they have very few abilities in combat. You want your opponents to attack your summons, so if you're using these as combatants you're kind of missing the point by a country mile.
Notable SLAs: Disguise Self at will, Vampiric Touch and Dispel Magic 3/day, and Mirror Image 1/day.
Final Evaluation: They're a niche pick, only useful for infiltration and seduction missions. They can be effective debuffers, but it's generally far too inefficient and convoluted to do so. Stick to heavy hitters unless you really need some guile on your side.

Kalabon
CR: 1/2
HD: 1
How to get it: SM II as a cleric of Glasya (replaces the lemure) or SM III as a LE caster (replaces fiendish ape)
Role: Minion
Fluff: These cancerous lumps of sodden flesh are spewed up from the remains of the Hag Countess. They are foul, barely intelligent creatures that nevertheless grow stronger and form oozing colonies when amassed. Easily controlled by the promise of relief from their psychic agony.
Advantages: Surprisingly damaging for a CR 1/2 summon, Kalabons also can sicken enemies around them. Multiple Kalabons can form larger, more damaging creatures. Fast Healing, too. Immune to acid.
Disadvantages: They pop like infernal pimples against the tiniest pinprick. No resistance to fire, either, so they're easily taken out by area attacks.
Notable SLAs: None.
Final Evaluation: Blech. A CR 1/2 creature from SM III? I cry foul. But they're clearly better than lemures, so I can understand the disparity. Still, I'd rule that these are summonable at SM II or even I, but RAW is not on my side here. The lower you can get them, the better they are - at III, they're not comparable to a Dretch or a Nashrou. As it is, I certainly wouldn't replace the ape with them.

Legion Devil
CR: 3
HD: 3
How to get it: None by RAW, likely SM IV
Role: Minion
Fluff: Highly organized and disciplined, Merregons are the rank-and-file infantry of hellish armies. They do things by the book and take orders extremely well. Act like a drill sergeant and they'll fall in line instantly.
Advantages: While an individual Merregon is nothing to write home about, they become exponentially better when grouped. They can't die unless the HP pool of all of them is depleted. If hit with an area effect or multiple target spell, all within 100' get to use the highest save in the group as their result (and good luck targeting one with mind-affecting spells, because they all get to try and save no matter which one was targeted). They get attack bonuses when grouped, too - +4 for each other Merregon within 60'.
Disadvantages: Their damage, unfortunately, doesn't improve in the proximity of others. Depending on your DM, you might not be able to use their Legion's Advance ability (while it is teleportation, it's a Su ability and not a [teleportation] spell - I personally wouldn't allow it as a summon, but some DMs might think differently). Legion's Mind has a drawback, too - if none of the devils make the save against a single target charm, they're all affected.
Notable SLAs: None.
Final Evaluation: Beautiful en masse, the Merregon is a tactical wonder. Individually, they're nothing to marvel over, but between your augmentation abilities and higher level slots, you can instantly create your own personal, brutally efficient army. Great at tanking and can form a veritable wall of swords.

Malebranche
CR: 14
HD: 16
How to get it: None by RAW, maybe SM IX
Role: Brute
Fluff: These dim-witted devils exist solely for brute force and shock troop tactics - they are beaten and bullied until they are completely obedient. "They exhibit an almost servile willingness to do whatever it is they are ordered to do, even if doing so means humiliation or death." Other devils sometimes use them as mounts. Total bootlickers.
Advantages: So, remember when I said that the Verakia was a melee monster? Well, the Malebranche gives them some heavy competition. They don't have as many options - they just attack, attack, and attack. But they do phenomenal amounts of damage at a good bonus. Huge with a good grapple score and an extremely fast fly speed (plus Flyby Attack). High DR, regeneration, and HP.
Disadvantages: Other than their fear aura (not very impressive), fighting is the only thing the Malebranche can do. Very low touch AC.
Notable SLAs: None.
Final Evaluation: Charge in, demolish things with your ranseur, end of combat. That's the Malebranche way - simple, brutal, and effective. If you can summon them, they'll have the highest damage potential in the SM IX line.

Narzugon
CR: 5
HD: 7
How to get it: None by RAW, likely SM V
Role: Brute
Fluff: Infernal cavalry, Narzugons ride into battle on nightmares. Unlike most devils, they dislike treachery and scheming, and are forthright, brave, and fearlessly loyal. These honorable warriors are probably the least likely to turn on you or betray you - they're noble, even tragic figures who might find some redemption in your service.
Advantages: If you're looking for some mounted warriors, they're good choices. They do respectable damage with their lances in a charge and can tank fairly well with high DR for their level and decent AC.
Disadvantages: Major issue: they don't come with a mount. So you have two choices: they can cast mount, which just gives them a generic horse, or you can use another spell slot to summon a Nightmare, which makes them basically badass. Their baleful gaze has a rather low DC.
Notable SLAs: Scorching Ray at will (just one ray, though) and Mount 3/day.
Final Evaluation: If you need to call in the cavalry, the Narzugon is a decent choice. Of course, you really only have two options: this or the Armanite. I prefer the Armanite because they are their own mounts, but the Narzugon has all the right feats for mounted combat while the Armanite does not. They're also a level or two lower, depending. A Narzugon on a Nightmare is a potent combination, though: charge in, breathe smoke to gain concealment, then retreat out to charge again.

Armanite
CR: 7
HD: 9
How to get it: None by RAW, likely SM VII
Role: Brute
Fluff: Armanites are demonic heavy cavalry. They live in packs led by leaders called knechts, plus they have their own cities. Seemingly socially organized, they still are known abandon their tasks in favor of extreme bloodlust. Give them the opportunity to charge into battle and they might submit to being bound.
Advantages: A powerful charge attack with lessened penalties, decent melee presence, and automatic Shocking Burst on arrows fired from their bows. Decent durability. Not a bad deal.
Disadvantages: Once they've charged, they're a little unimpressive in melee for their level. No abilities outside of straight melee.
Notable SLAs: Airwalk for an hour/day.
Final Evaluation: Fairly run of the mill. Decent in melee (but only decent) and not much else. While I like the charge, the Bulezau later on in the same book are much better at it for just a single SM level.

Bar-lgura
CR: 5
HD: 6
How to get it: None by RAW, likely SM V
Role: Overlord
Fluff: Looking like gigantic fiendish orangutans, Bar-lgura are demonic scouts and skirmishers. They are rather odd - though they still craft grim totems and fetishes and despise most other beings, they don't take nearly as much pleasure in torment and suffering as other demons. In fact, they consider other demons a nuisance and despise working with them. Could be twisted to your advantage.
Advantages: Quite mobile, with good SLAs and a decent attack schedule. While summoning them won't let you take advantage of it (you'd have to use Lesser Planar Binding), their Abduction ability is basically an at-will teleportation taxi service, two party members at a time. Pounce, too!
Disadvantages: Melee damage does leave something to be desired at this level, though they are better than the Bearded Devil at SM V. They pale in comparison to the fiendish giant crocodile, unfortunately.
Notable SLAs: Telekinesis, Dispel Magic, and Cause Fear at will, plus Major Image, Invisibility, and Disguise Self 2/day.
Final Evaluation: I like Bar-lgura quite a bit. They are a bit like the jacks-of-all-trades of the demonic realms. They can be sneaky, tactical, brutish, or a mobile assault platform with telekinetic ammunition. The lowest level Overlord. They're not always your best choice, but they're always a good choice. A great choice for a LPB.

Broodswarm
CR: 6
HD: 8
How to get it: None by RAW, likely SM VI
Role: Minion/Manipulator
Fluff: Broodswarms are deathly loyal swarms formed by night hags in an agonizing ritual. They exist only to seek out potential souls for the night hag to transform into larva. They attack good souls almost exclusively. You can summon or bind one, but you'll likely incur the wrath of its night hag mother.
Advantages: Swarm traits can be handy. Their Daze and Stitching (Stitching has no save!) abilities, in combination with the Distraction swarm trait, make them potent disablers. A blind, mute, helpless, dazed enemy is a good enemy. A swarm with Evasion is a very good combination, too.
Disadvantages: If an area effect hits 'em, kiss 'em goodbye. Their damage is very low. Stitching offers a fairly easy Strength check to break out, though each attempt does damage.
Notable SLAs: None.
Final Evaluation: A niche pick, particularly when you want to disable and/or capture foes rather than killing them. Not all that effective for its level, unfortunately.

Bulezau
CR: 9
HD: 10
How to get it: None by RAW, likely SM VIII
Role: Brute
Fluff: Goat-headed shock troops and formation assault squads of the Abyss. They are difficult to control and fly into berserk rages. Bulezau only obey orders under the threat of death from a more powerful overlord - otherwise they fall into immediate chaos and frenzied battle. Impress them with your power and they'll fall in line.
Advantages: Melee monsters. Their ranseurs are very damaging with 20' reach, and even their charge pales in comparison to it. That said, the charge is still quite good. A good complement of SLAs.
Disadvantages: Their SLA save DCs are pitifully low. Their BAB could use a boost, too. Their AC makes me sad, but you want them to get hit.
Notable SLAs: Solid Fog and Telekinesis at will, Fear 3/day and Shout 1/day.
Final Evaluation: I'm a reserved fan. A decent source of damage in melee, but the Vrock is still a more consistent choice at this level with its better attack bonus and other abilities. Of course, the Bulezau's Sense Motive is nonexistent, so it's easier to trick. Solid Fog is, however, a good ability to have at will, so it's a toss-up.

Chasme
CR: 10
HD: 9
How to get it: None by RAW, likely SM VIII
Role: Assassin/Caster
Fluff: Chasmes are abyssal torturers and slavemasters, thrilling in pain and suffering. They despise all other demons (and probably you too), but will temporarily ignore their predilections if offered the chance of torture or interrogate others.
Advantages: First off, they're swift and perfect flyers with Flyby Attack and attacks that cause bleeding wounds. They have a good full-attack schedule at an acceptable BAB. They have a vast array of useful SLAs.
Disadvantages: Their auras aren't all that helpful (who cares about sleep at level 15?) and they don't do a whole lot of damage with their attacks.
Notable SLAs: Contagion, Dispel Magic, Fly, Insect Plague (bind only), Ray of Enfeeblement, See Invisibility, and Telekinesis at will, plus Quickened Ray of Enfeeblement 3/day.
Final Evaluation: Hard to find a lot wrong with the Chasme. Sure, there are plenty of aerial skirmishers in the demonic catalogue, but none of them have the Chasme's magical abilities nor as much damaging potential. Great at SM VIII, decent at SM IX.

Dybbuk
CR: 8
HD: 10
How to get it: None by RAW, likely SM VII
Role: Manipulator/Caster
Fluff: Creepy incorporeal loumara (a subtype of demon) that possess the dead for perverse, hedonistic purposes. They constantly are on the search for that perfect body, a fresh, attractive corpse whose death no one has yet noticed. Perhaps they will find such a corpse among your enemies?
Advantages: They can corpse-hop amongst the remains of your enemies, which has a lot of potential if you take down the strongest foe first, then let its possessed corpse turn on its former allies. It has an interesting Death Touch ability (though far too easy to resist), and it can impart a profane 24-hour bonus to mortals. Does 1d6 Con damage with its tentacles, healing itself at the same time.
Disadvantages: Possessing corpses is rather a niche skill, don't you think? If there's nothing dead to take, the Dybbuk's power is significantly lessened. By the time you can summon one, 1d6 Con damage isn't going to change the board much (though it's not bad), and its SLAs are shut down cold by Mindblank.
Notable SLAs: Obscuring Mist at will, plus Fear, Phantasmal Killer, and Mind Fog 3/day.
Final Evaluation: An interesting bit of potential, I still find the Dybbuk too much a situational choice to rely on. I want summons that can kill things, not control things that are already dead.

Ekolid
CR: 4
HD: 5
How to get it: None by RAW, likely SM V
Role: Assassin
Fluff: Intelligent insectile abominations who reproduce by implanting their eggs into as many creatures as possible, Ekolids have little motivation beside reproduction. Those under the rule of Obox-Ob form vast hive-cities made out of corpses. Man, Obyriths are creepy.
Advantages: Seven attacks per round! Their eggs do extra damage and nauseate their victims. They get to take an extra move action, and have a 60' average fly speed.
Disadvantages: Their aura can really mess up your party, causing a -1 on all skills and forcing casters to make a concentration check to cast even the simplest spells (though at DC 10, any half-way optimized caster should beat it). Somewhat fragile, and does poor damage. Awful grapple modifier.
Notable SLAs: None.
Final Evaluation: Eh, I think the risk outweighs the reward here. Still, they can do a good bit of damage to mooks with their incubation abilities. Pretty much a pass.

Goristro
CR: 16
HD: 24
How to get it: Implore
Role: Brute
Fluff: Living seige engines, the bestial Goristros are nasty, brutish, and enormous. They live only to destroy and devour, and are too dumb to be enticed by wealth or power. All they want to do is hit things until they stop moving, and then eat them. Offer them that.
Advantages: A pair of accurate, powerful slam attacks. Loads of HP. Good DR and Fast Healing. They can mimic earthquakes by stomping. Their feats make them ideal for battering down citadels and walls, or just tossing aside mooks like bowling pins.
Disadvantages: Supposedly not easily controlled or directed in battle. Abysmal touch AC. A puzzlingly high Sense Motive skill.
Notable SLAs: Fear, Levitate, and Spider Climb at will.
Final Evaluation: Well, they're certainly good at beating the crap outta things, though I wish they had more attacks. Though they're titanic bruisers, the hoops you have to jump through to obtain one makes them not quite worth the trouble - if I'm going to use Implore for a dumb bruiser, I'd rather have the Ghargatula or a brutish Aspect. Still, there's no way to wade into battle more stylishly than on a palanquin mounted on a Goristro's head.

Guecubu
CR: 4
HD: 4
How to get it: None by RAW, likely SM V
Role: Manipulator
Fluff: Disembodied abyssal spirits who believe that their serial murders form a pattern that will reveal the nature of the multiverse. Cruel and merciless, but somewhat weak.
Advantages: Incorporeal and naturally invisible, Guecubu make great scouts. They can also possess sleeping creatures and use Telekinesis while inhabiting another body, giving them as much possibility as you can imagine.
Disadvantages: No source of damage outside of Telekinesis. Fairly low HP. Unless you are careful when commanding it, it might decide to possess you.
Notable SLAs: Telekinesis at will.
Final Evaluation: Supreme infiltrators, Guecubu are useful in a host of non-combat situations. They're just not that useful in combat. Situational, but quite good in the right situation.

Laghathti (Web Enhancement)
CR: 10
HD: 12
How to get it: None by RAW, likely SM VIII
Role: Manipulator
Fluff: Ancient mind-wiping tentacle beasts, Laghathti love nothing more than stealing agonizing or tragic memories and implanting terrifying memories into unsuspecting minds. They're not very bright, preferring to pore over their collection of memories rather than think for themselves. If the villains you face have particularly tragic backstories, perhaps a Laghathti will consent simply for the chance to steal their remembrances.
Advantages: Seven attacks a round at a decent bonus, each one with the chance of bestowing a negative level. That's some mighty fine debuffing right there, plus it can pounce. Fast Healing, DR, and high HP make it a durable choice as well. Very good senses, too, with all-around vision and true seeing.
Disadvantages: Oof, 2d4 negative levels just by looking at the thing is a hefty mark against it. On land, they're a bit sluggish. A very limited selection of SLAs.
Notable SLAs: Modify Memory at will.
Final Evaluation: Like all Obyrith, the Laghathti poses a significant risk to you simply by summoning it. This one is potentially the worst offender of the bunch. Still, if you can get your hands on something that gives you immunity to negative levels (immunity to negative energy won't work, since the ability specifically says "These negative levels do not result from negative energy"), it's a very potent disabling grappler.

Lilitu
CR: 12
HD: 14
How to get it: None by RAW, likely SM IX
Role: Caster
Fluff: The succubus MK II, a Lilitu specializes in the corruption of mortal churches and priests. They used to be succubi, until a ritual which claims the life of an entire congregation burns their wings away and transforms them into the hideous mockeries they are now.
Advantages: They get to cast as a 9th level cleric, which is very handy. Great SLAs. A helpful poison on its tail sting (negative levels and WIS drain). It's not exceptional in combat - but out of it, the interrogative powers are limitless. Automatic UMD success. They can also imbue a recipient with a profane +2 bonus to CHA and saves.
Disadvantages: Pitiful damage and a severe weakness to divine magic. Very easily dealt with by a cleric or druid who sees through her trickery. Extremely high CHA, so it's going to be a long and bumpy road to Planar Binding. That profane bonus she can impart lets her track you at all times, so beware retribution.
Notable SLAs: Charm Monster, Fly, Suggestion, Sending, and Disguise Self all at will, plus Dominate Person, Quickened Suggestion, and Symbol of Persuasion 1/day. Their cleric spells include beauties like Bestow Curse (helpful if you banned Necromancy), Confusion, Lesser Planar Binding, and Raise Dead.
Final Evaluation: With a host of spells and SLAs, Lilitu can really shore up your weaknesses in the casting department. I find them extremely useful when coercing a trapped creature into a contract - sting them for negative levels, curse them, and dominate them into agreement. Delightful.

Mane
CR: 1
HD: 1
How to get it: None by RAW, likely SM II
Role: Minion
Fluff: Pathetic husks of mortal souls sent to the Abyss, Manes exist only to be tortured, ravaged, and abused. One of the only things that scares demons is the threat of being demoted and twisted into a Mane.
Advantages: They do have one extra attack on the Lemure. Plus, they explode in a caustic damaging mist, which can turn them into walking, dying, exploding flasks of acid.
Disadvantages: Just about everything - crappy HP, AC, and damage.
Notable SLAs: None.
Final Evaluation: A slightly better pick than the Lemure, it's still SM II. Don't expect much.

Molydeus
CR: 19
HD: 19
How to get it: GPB
Role: Overlord
Fluff: The Molydeus is a lord among demons, usually seen to be on an equal standing with the Balor. Mostly, it spends its time seeking out renegade demons (technically aren't all demons renegades?) and deserters and exact righteous punishment. Extremely feared by other demons for its ability to transform them into manes. It is an arrogant spellcaster who attempts to subdue a Molydeus, as they only suffer orders from the Lords of the Abyss. Tough, tough bind, and the Molydeus will likely turn on you in an instant.
Advantages: They do more damage than a Balor (though their attack bonus is slightly lower) and outstrip the other demon in terms of AC and Fast Healing. Fast Healing 30, by the way. Insane. They get to ignore most forms of damage reduction and have a devastating poison attack that even affects those who are immune to poison.
Disadvantages: Their SLA selections are underwhelming. With 28 CHA and the +31 Sense Motive, good luck binding them.
Notable SLAs: Baleful Polymorph, Vampiric Touch, Fear, and Suggestion at will; Dimensional Lock and Lightning Bolt 7/day, quickened Telekinesis 3/day, and Trap the Soul 1/day.
Final Evaluation: I like the Molydeus. Maybe not necessarily more than the Balor, but it's certainly comparable. Slightly better in melee, but slightly worse casting. Really, if you manage to bind either of them, you're golden.

Nabassu (juvenile, mature)
CR: 5, 15
HD: 5, 15
How to get it: None by RAW, likely SM V for juvenile; GPB for mature
Role: Assassin
Fluff: Nabassu are gargoyle-like demons with a noted predilection for undead creatures, graveyards, and negative energy. They grow by consuming mortals from the Prime, retreating back to the Abyss to form their own dominions once they've devoured enough. Mature nabassu are particularly greedy.
Advantages: The juvenile is a decent enough combatant, with 2d6 sneak attack damage and three attacks. It also has a level-draining gaze. The mature steps it up further, giving us a host of SLAs, 6d6 sneak attack damage, and regeneration. Both have the option of feeding, gaining bonuses and preventing the enemy from being easily raised.
Disadvantages: Their AC is a bit low and they rather annoyingly don't have Flyby Attack.
Notable SLAs: Obscuring Mist and Darkness at will for the juvenile; Enervation, Ethereal Jaunt, Greater Dispel Magic, Hold Monster, Obscuring Mist, Silence, and True Seeing at will, plus Energy Drain and Blasphemy 3/day for the mature.
Final Evaluation: I'm a little worried about that level-draining gaze, as it could potentially turn on you and yours. Overall though, whether summoned or bound, I find the Nabassu to be an interesting choice of assassin. They can rip things apart in melee and provide solid debuffs against the enemies they can't touch.

Rutterkin
CR: 3
HD: 5
How to get it: None by RAW, likely SM IV
Role: Minion
Fluff: Deformed foot soldiers and bestial brutes, Rutterkin understand very little but physical force and intimidation. They are savage and merciless towards anything they perceive as weaker.
Advantages: Sadly, not a ton to love here. They're much weaker than the fiendish dire wolves of the same level. The only point in their favor is their automatic grappling reach weapons, but even those aren't much to get excited about. I suppose they're also reasonably durable.
Disadvantages: Low attack, low damage, and a low grapple modifier make Rutterkins bad at their primary function.
Notable SLAs: Cause Fear at will (though the Dretch is a level lower and casts a better version).
Final Evaluation: Bad SLAs, no abilities, and a poor showing in melee, which is really the only thing they can do. Don't linger here. Pass.

Sibriex
CR: 15
HD: 15
How to get it: GPB
Role: Manipulator/Caster
Fluff: These gigantic ugly floating heads (god, the stuff of nightmares) are the living, sentient spawning pools of the Obyrith, fleshcrafters and insane twisted biologists. They are quite vain and desire complements of guards to protect and fawn over them. They are highly intelligent and domineering.
Advantages: Well, they can create and attach fiendish grafts for free! In case you wanted them. They have a decent host of enchantment-based SLAs, and they can cover enemies in acidic bile.
Disadvantages: Crappy speed and pathetic dexterity, plus they drive everyone around them insane. Fortunately, it's not as damaging of an insanity as other Obyrith, but it's still a bad idea. 25 CHA makes it hard to bind.
Notable SLAs: Hold Monster, Charm Monster, Major Creation all at will, plus Feeblemind 3/day.
Final Evaluation: I don't personally like them, as they are too given to scheming and betrayal, especially when their aura of insanity cripples your saves against their charms. Still, free grafts might appeal to some, and it can hold its own in combat.

Yochlol
CR: 8
HD: 10
How to get it: None by RAW, likely SM VII
Role: Assassin
Fluff: These are the handmaidens of Lolth, her chosen attendants. They are unparalleled tricksters and shapeshifters. They're favored daughters of their goddess, and they know it - they're disdainful and cruel towards all others, demons included. Summoning and binding them may rub Lolth the wrong way - bad idea.
Advantages: Four distinct forms that offer all sorts of advantages in infiltration. They can turn into a Stinking Cloud, a beautiful female humanoid, a spider (with Con damaging poison), or their natural jelly form. Eight attacks a round, plus a nice array of SLAs. CHA bonus to saves and AC, plus permanent Mind Blank.
Disadvantages: Pathetic damage with their tendrils. Low AC. The aforementioned "Favored of Lolth" thing.
Notable SLAs: Dominate Person, Stone Shape, Web, and Spider Climb at will.
Final Evaluation: I like them for their potential in disguise, infiltration, and information-gathering, but step carefully around your DM with them - he may decide to bring the Lolth-hammer down on you.

Alkilith
CR: 10
HD: 11
How to get it: None by RAW, likely SM VIII
Role: Brute/Caster
Fluff: Disgusting amorphous slime demons, Alkiliths are reviled by most other demons and only called upon in the direst of situations. They love to defile their surroundings with their own foul corruption.
Advantages: They do decent damage with their acidic pseudopod attacks, have a sizable collection of useful SLAs, and they have respectable defenses due to their amorphous nature. They can transform into a Cloudkill spell, which has its uses. They can command oozes as a free action.
Disadvantages: Their acidic attacks will melt your treasure! And while the repeating nature of the damage is nice, it takes a while to really add up.
Notable SLAs: Contagion, Enervation, Stinking Cloud, and Wall of Ice at will, plus Cone of Cold 3/day.
Final Evaluation: While Alkiliths are capable and have some interesting abilities, they violate one of the cardinal rules of the game: thou shalt not damage your own potential treasure! Still, against treasureless enemies, Alkiliths may be a minor boon. Otherwise, keep them out of melee and let them act as artillery with Cone of Cold.

Blood Fiend
CR: 14
HD: 12
How to get it: None by RAW, maybe SM IX
Role: Manipulator
Fluff: Blood Fiends are basically the demon equivalent of vampires. No, not basically - they are demonic vampires. They're undead. Nearly all of their abilities are vampiric in nature. The only difference is that instead of namby-pamby hedonistic glistening pretty boys, they are nine feet tall, have four viciously clawed arms, and have gigantic maws filled with rows upon rows of razor-sharp teeth. These guys make vampires crap themselves.
Advantages: Decent Domination gaze. They have four attacks that drain levels, and they can drain Con with their bite attack. Undead traits and Gaseous Form add to survivability.
Disadvantages: For a CR 14 creature, they have a pathetic attack bonus. SLAs are booooring.
Notable SLAs: Extremely stereotypical demon selection - Detect Magic at will, plus Chaos Hammer, Darkness, and Unholy Blight 3/day, plus Blasphemy and Desecrate 1/day.
Final Evaluation: Blah. I don't want to summon vampires, let alone demonic vampires. They're handy for their gaze, but that's about it. I get the vampiric theme, but it's just not an effective pick. Oooh, look, they can turn into Howlers or Nightmares? Well I can summon those already, and at a much lower level.

Klurichir
CR: 17
HD: 20
How to get it: GPB
Role: Overlord
Fluff: They give balors nightmares supposedly. They're gigantic winged generals and majordomos for the mightiest Abyssal lords. They don't take no crap. They are brilliant and visionary tacticians, but they prefer to stand back and let their minions do their work for them. Convincing one to become your minion will be one hell of a challenge.
Advantages: While they do have a satisfying attack schedule and vorpal stomach pincers (they make excellent grapplers, but that's kind of wasting their potential), these guys are all about the spells. In addition to their SLAs, they also cast as a 10th level sorcerer. If you can get some spell picks swapped around (they apparently prefer evocation/abjuration, but there's no reason why every Klurichir has to have the same list), that feature can end up quite useful.
Disadvantages: At 23 CHA, they are a difficult bind, but they are easier than a Balor for some reason. The typical list given for their sorcerer spellcasting is kind of awful - who's casting Fireball at this point?
Notable SLAs: Greater Dispel Magic, Wall of Fire, Symbol (any), and Unholy Aura at will, plus Implosion, Destruction, Enervation, Fire Storm, and Slay Living 3/day. Plus sorcerer spellcasting - typical picks are Dismissal, Ice Storm, Stoneskin, Fireball, Haste, Protection from the Elements, Protection from Arrows, Melf's Acid Arrow, Endurance, Flaming Sphere, and Magic Missile.
Final Evaluation: Oddly enough, the Fiendish Codex I bumped their CR down from 25 to 17, so I don't know if they technically give Balors nightmares anymore. But they can automatically summon two Balors. You bind a Klurichir, it summons two Balors. A CR 17 creature summoning two CR 20 creatures seems consummately broken. One of the best binds possible, if only for that reason. Add in the supremely useful SLAs, and there's no good reason not to give it a shot.

Maurezhi
CR: 3 (Bah!)
HD: 5
How to get it: None by RAW, likely SM V
Role: Caster/Assassin
Fluff: Demonic versions of ghouls (sensing a theme with the Fiend Folio?), Maurezhi aren't technically undead. They are however corpse-eaters and shapechangers, taking on the guises of those that they consume. They exist solely to devour corpses, fulfilling their insidious urges.
Advantages: They can advance by consuming humanoids, which makes them a potential long-term scaling companion. They have a paralyzing attack. They steal the memories of those they eat, which can be helpful for infiltration.
Disadvantages: Crappy attack, middling HP, and general poor combat abilities means that the Maurezhi is basically designed to sit back and create an undead army.
Notable SLAs: Hold Person, Animate Dead, Blur, and Death Knell at will.
Final Evaluation: I don't buy FCI's drastic CR reduction here. I still put Maurezhis around CR 5-6. Animate Dead at will is a handy ability for army generation, and they're no pushovers. I like their advancement and I like their abilities. They're not very useful as a summon, since they take ten minutes to eat corpses, but as a lesser bind they're not a bad choice.

Myrmyxicus
CR: 18
HD: 18
How to get it: GPB
Role: Overlord
Fluff: Myrmyxicuses (god what a horrible name to spell repeatedly) are the lords and masters of the foreboding Abyssal Ocean depths. They carve their own citadels out of bone and coral and balk at serving any but themselves. Likely, they won't tolerate your harness for long.
Advantages: They do some decent damage with their unholy scythes. They can breathe unholy vapor that heavily damages good creatures (again, not that useful except in certain campaigns).
Disadvantages: For supposed high-level overlords, they have some pretty lackluster SLA options. They're aquatic, though as outsiders they don't need to breathe. But still, they're sluggish when not in water.
Notable SLAs: Charm Person and Telekinesis at will, plus Control Weather, Control Water and Greater Dispel 3/day.
Final Evaluation: Well, really effective against good creatures with their various unholy abilities. Unfortunately, they have very little to offer outside of an aquatic campaign. I don't like 'em. Better options for GPB.

Skulvyn
CR: 4
HD: 5
How to get it: SM IV
Role: Brute
Fluff: Bestial predators that roam Abyssal seas in schools looking for lesser beings to prey upon, Skulvyns are little more than animals. Should be extremely easy to bully or bluff.
Advantages: Well, I like the wounding properties of the tail lashes, as Skulvyns can fire off four of them a round, and those wounds add up. They're decent in melee for their level. The slow aura is handy, too.
Disadvantages: Unfortunately, the slow aura has a pitifully low DC. On land, they are extremely sluggish.
Notable SLAs: None.
Final Evaluation: A niche pick, mostly for aquatic campaigns. As long as you summon them near your enemies, their slow aura and wounding tail lashes might make for an effective choice, but my gut instinct is to give 'em a pass.

Wastrilith
CR: 11
HD: 15
How to get it: SM IX
Role: Caster
Fluff: Like Myrmyxicuses, Wastriliths are lords of the seas and waterways of the Abyss. They seem to be lesser lords, and are likely subservient to their betters. Wastriliths have a nasty habit of forcing others to serve them, and have developed the ability to deceive summoners easily. They really like pirates for some reason?
Advantages: Blargh. Not much, especially at this level. Okay SLAs. Decent mobility, even on land.
Disadvantages: Um. They can immediately break a summon with an opposed Wisdom check. If you're a wizard summoner, you're absolutely screwed. Even if you're a cleric, they're still not worth the risk. Crappy melee.
Notable SLAs: Control Water, Blasphemy, Wall of Ice, and Telekinesis at will, plus Symbol (any) 3/day.
Final Evaluation: No, no, no, no, no, Even without considering anything else, I still balk at the Break Summoning ability. But pretty much everything else sucks, too. Paaaasss. Pass so hard.

Artaaglith
CR: 6
HD: 5
How to get it: SM VI
Role: Caster
Fluff: Servants of Orcus who live to create undead abominations and guide them into battle, Artaaglith are necromantic clerics extraordinaire. Offer them the opportunity to create undead armies for their foul master (a dubious act on your part) and they might serve you. Heaven forbid your purposes and Orcus' align, however.
Advantages: They cast as a 5th level cleric and have a decent array of SLAs. Ghostwalk doesn't give them a spell list, so their cleric spell choices are potentially up to you. They can actually turn undead, which can come in handy.
Disadvantages: Disappointing in melee with a rather middling Con score, Artaaglith are really only useful for their clerical casting.
Notable SLAs: Animate Dead, Cause Fear, and Stinking Cloud 1/day.
Final Evaluation: They're certainly decent for their level, and if you need some clerical backup or a quick squadron of undead, they're a nice choice. Still, they're not very good at anything else. In a campaign heavy on undead, they can be quite useful - in other campaigns, they're still decent, but their strengths aren't being utilized effectively.

Uridezu
CR: 6
HD: 7
How to get it: None by RAW, likely SM VI
Role: Assassin
Fluff: Demonic errand-boys, Uridezu have an affinity with rats and are commonly found on the Material Plane. They are apparently desperate to please their masters and will go to any length to serve (a nice bonus for you).
Advantages: Um... they have a whip for a tail? They can paralyze, at least.
Disadvantages: Boo to them not having Sneak Attack. Or any legitimate method of dealing damage in melee. To be honest, Uridezu basically suck. Pathetic AC (15!?). Poor HP. For a rogue-like summon, they have really crappy skills, too!
Notable SLAs: Unholy Blight 1/day.
Final Evaluation: There's simply nothing to recommend them to anyone, unless you somehow need to befriend rats. They suck at basically everything. Stay far, far, far away. One of the worst summons yet. Fiendish Codex I keeps them at CR 6, which I think is a mistake. They're really more like CR 3.

Shadow Demon
CR: 8
HD: 10
How to get it: None by RAW, likely SM VII
Role: Assassin
Fluff: Shadow demons are incorporeal creatures formed out of the very evil essence of the Abyss itself. They rarely obey others, preferring to serve their own incalculable whims. They often choose to serve mortals, however, if they are offered the chance to harvest a great many soul - but they'll likely want to harvest yours as well.
Advantages: First off - Magic Jar! This spell is awesome. I do so love jumping around from foe to foe, causing havoc and mayhem while preventing any of them from knowing just what the hell is going on. They get +4 to just about everything wihle in darkness, which is a nice bit of scale-tipping. Quick and mobile, with a perfect fly speed. Phenomenal Hide and Move Silently.
Disadvantages: While the Vile damage aspect of their attacks are nice, they don't do a whole lot of damage. Awful light sensitivity. Quite fragile, too. Magic Jar is only once a week, which severely limits its long-term potential.
Notable SLAs: Darkness at will, plus Deeper Darkness and Damning Darkness 1/day, plus Magic Jar 1/week.
Final Evaluation: Lots of fun. They make consummate ambushers with their darkness abilities, and when in doubt, use Magic Jar. A few shadow demons possessing nearly all of your enemies at once and forcing them to all demolish each other is a sight to be seen. An excellent choice for general mayhem.

Cerebrilith
CR: 10
HD: 9
How to get it: None by RAW, likely SM VIII
Role: Caster
Fluff: These psionic demons are really only brought into the fold when needed to combat mortal psions - otherwise, they spend their time dissecting brains and fortifying their own psychic strength. They love to attack intelligent foes, so if you can offer them a powerful wizard or psion as a target, they might be inclined to obey. Just don't betray your own intelligence to them.
Advantages: A host of interesting PLAs make the Cerebrilith primarily a psionic caster. They're reasonably durable with a high AC.
Disadvantages: Poor in melee when not psionically focused.
Notable PLAs: Brain Lock, Detect Psionics, Ego Whip, Id Insinuation, and Mind Trap at will, plus Psionic Dominate, Ectoplasmic Form, and Mind Probe 3/day, plus Mind Thrust 1/day.
Final Evaluation: They're one of your only options for a non-Eberron psionic caster. They're quite good at what they do, though their blasting capabilities aren't at the same level as the quori described later in the guide.

Abyssal Eviscerator
CR: 4
HD: 4
How to get it: None by RAW, likely SM V
Role: Brute
Fluff: Surprisingly intelligent (relatively) bruisers who roam in Abyssal warbands, Eviscerators are large and in charge. So to speak. Actually, you're in charge. Of them. Because they're weak and kind of dumb.
Advantages: Um. They do damage? They do actually have a decent attack bonus.
Disadvantages: Weak damage for the level (Nashrou are still better), they also have no DR, hardly any abilities.
Notable SLAs: None.
Final Evaluation: Like the Carnage Demon, they're built for one purpose (combat) and then aren't very good at that purpose. A boring choice with little to recommend it.

Ghour
CR: 12
HD: 12
How to get it: None by RAW, likely SM IX
Role: Brute/Manipulator
Fluff: Servants of the minotaur lord Baphomet, Ghours run rampant through labyrinths and underground passages and ruins. They're big and intimidating, but they lack subtlety or finesse - things you'd better have in spades.
Advantages: Passable melee and a hefty grapple bonus, Ghours are made for close-quarters combat. They can emit a noxious cloud of strength-draining gas or emit an stunning roar. For a supposed bruiser, they have some nice SLAs, though often just to make themselves better bruisers (Righteous Might? Oh yeah).
Disadvantages: Their damage is a little underwhelming and they have poor reflexes and reactions.
Notable SLAs: Confusion, Maze, and Righteous Might 3/day.
Final Evaluation: Ghours are a great choice for bruisers. While the Jarilith is used when you need pure raw damage, Ghours should be used when you need a little more situational control - their SLAs give them an extra edge in combat. Between their stun, Maze, and Confusion, they can easily lock down a battlefield for you.