Hey Sinfire, at your suggestion I made a couple of Commander decks. Having never built them before, I'm not really sure what kind of strategies to use. Thoughts? Also, I'd love a Commander game at some point.
1 Trace of Abundance
1 Gloryscale Viashino
1 Godsire
1 Knotvine Paladin
1 Knotvine Mystic
1 Johan
1 Mirari's Wake
1 Naya Hushblade
1 Titanic Ultimatum
1 Apocalypse Hydra
1 Blitz Hellion
1 Hull Breach
1 Deus of Calamity
1 Firewild Borderpost
1 Fossil Find
1 Rip-Clan Crasher
1 Rosheen Meanderer
1 Shivan Oasis
1 Autochthon Wurm
1 Eladamri's Call
1 Enlisted Wurm
1 Heroes' Reunion
1 Hunting Grounds
1 Knight of New Alara
1 Phytohydra
1 Privileged Position
1 Mayael the Anima
1 Mayael's Aria
1 Congregation at Dawn
1 Pure // Simple
1 Reborn Hope
1 Steward of Valeron
1 Tolsimir Wolfblood
1 Wildfield Borderpost
1 Wilt-Leaf Cavaliers
1 Sarkhan Vol
1 Ajani Vengeant
1 Ajani Goldmane
1 Chandra Ablaze
1 Chandra Nalaar
1 Chandra, the Firebrand
1 Garruk Wildspeaker
1 Garruk, Primal Hunter
1 Elspeth Tirel
1 Elspeth, Knight-Errant
1 Nissa Revane
1 Gideon Jura
1 Koth of the Hammer
1 Balefire Liege
1 Boros Garrison
1 Boros Signet
1 Bull Cerodon
1 Cerodon Yearling
1 Figure of Destiny
1 Hearthfire Hobgoblin
1 Lightning Helix
1 Razia's Purification
1 Razia, Boros Archangel
1 Skyknight Legionnaire
1 Waves of Aggression
1 Brushland
1 Elfhame Palace
1 Savannah
1 Sungrass Prairie
1 Tranquil Garden
1 Arctic Flats
1 Temple Garden
1 Selesnya Sanctuary
1 Wooded Bastion
1 Sunpetal Grove
1 Graypelt Refuge
1 Stirring Wildwood
1 Battlefield Forge
1 Plateau
1 Platinum Emperion
1 Platinum Angel
1 Scabland
1 Ancient Amphitheater
1 Ancient Ziggurat
1 Sacred Foundry
1 Rugged Prairie
1 Mossfire Valley
1 Taiga
1 Karplusan Forest
1 Pinecrest Ridge
1 Highland Weald
1 Stomping Ground
1 Gruul Signet
1 Gruul Turf
1 Fire-Lit Thicket
1 Rootbound Crag
1 Kazandu Refuge
1 Raging Ravine
1 Selesnya Signet
2 Forest
2 Mountain
2 Plains
Couple of things for the Cockatrice version:
A suggestion I make to everyone playing an aggro-deck: Kozilek or Ulamog. You need a way to recycle your graveyard because you will get hit with Wrath effects a lot.
As far as mana rocks go, the Borderposts are fairly bad in EDH (especially with only 6 basic lands).
Apocalpyse Hydra isn't very useful with Mayael's ability, in spite of the fact that it is Naya-oriented. X spells in general aren't that good for Mayael.
I'm seeing a large number of very inefficient beaters. Specifically, Autochthon Wurm, Blitz Hellion, Bull Cerodon, Cerodon Yearling, Gloryscale Viashino, Godsire, Hearthfire Hobgoblin, Johan, Knotvine Paladin, Naya Hushblade, Phytohydra, Razia, Rip-Clan Clasher
Skyknight Legionnaire, Tolsimir Wolfblood, and Wilt-Leaf Cavalier.
Some suggestions for replacements:
Elesh Norn, Grand Cenobite (game-ending pump effect, capable of annihilating certain strategies while protecting you)
Sun Titan (able to reanimate Mayael, Witness, and other permanents. All else fails, you can get back lands and have a second Prime Titan)
Bogardan Hellkite (Solid creature, capable of nuking weenies or taking out a chunk of life from an opponent, or divide the damage up for a strategic play)
Inferno Titan (Effectively a 9/6 for 6, but it has never failed to be a death threat)
Acidic Slime (One of the best removal effects you have)
Avenger of Zendikar (If it sticks through Mayael, you can win the game in short order)
Eternal Witness (Like Sun Titan, this is a valuable piece of recursion)
Primeval Titan (One very efficient beater)
Spearbreaker Behemoth (Helps set up your board in case you can't use Mayael)
Terastodon (Abuse-able with something like Emeria or another reanimator effect)
Vigor (Protects your board while making your creatures more efficient threats. Combine it with Earthquake or similar spells)
Vorinclex, Voice of Hunger (Back-breaking)
Woodfall Primus (A big brother to Acidic Slime)
Gadock Teeg (Another board-protecting card)
Blightsteel Colossus (Game-ending)
Steel Hellkite (Removal is vital to any deck, and this likes Mayael)
This raises your deck to a fairly steep curve, but that's easily solved via good mana acceleration (which you have access to).
Given that you don't have that many X spells (and I've suggested Teeg), I don't think Rosheen will be very helpful.
Hunting Grounds and Trace of Abundance aren't that efficient. The latter because it's an aura and prone to being a casualty in a sweeper, and the former because threshold is not something you want to achieve. Some suggestions (pick to; most of them are more expensive, but are more likely to help you out):
Call of the Wild (Works with Sensei's Top)
Cream of the Crop (Really works with Mayael)
Lurking Predators (Same effect, no Threshold).
Oath of Druids (If dropped early, it can mean the game falls into chaos)
Impromptu Raid (Low-profile compared to Lurking Predators, but not as efficient as Call of the Wild due to the Sacrifice)
Killer Instinct (Same idea as the Raid, less mana-intense)
Animal Magnetism (Political, but it can work)
Birthing Pod (Requires some build effort)
Genesis Wave (Resolving this for 7 or more means you are likely to get three very big creatures out for one spell, along with some solid drops)
Mana Reflection (It wins games)
True Conviction (It is capable of putting you far ahead of your opponents)
Heroe's Reunion and Lightning Helix are bad in EDH. Replace the former with Beast Within and the latter with Decimate.
Cut down on the Planeswalkers. Namely, Chandra Ablaze (you lack red instants and sorceries), Elspeth Tirel (she's shit in almost every format, and only played in Standard because the Token deck is really good), Koth of the Hammer (you are playing three colors), and Nissa Revane (you are not running anywhere near enough elves to justify her, and I hate her with a fiery passion). Possibly Ajani Vengeant too, but he's actually capable of winning a game.
Cut Fossil Find, Pure//Simple, Reborn Hope, and Waves of Aggression.
Some spells that will help:
Hunting Wild
Cultivate
Explosive Vegetation
Kodama's Reach
Realms Uncharted
Reap and Sow
Sylvan Scrying
Farseek
Some help fixing your mana base:
Plateau
Savannah
Taiga
Sacred Foundry
Stomping Ground
Temple Garden
Arid Mesa
Windswept Heath
Wooded Foothills
Fire-Lit Thicket
Rugged Prairie
Wooded Bastion
Clifftop Retreat
Rootbound Crag
Sunpetal Grove
Gavony Township
Kessig Wolf Run
Sunhome, Fortress of the Legion
Command Tower
Reflecting Pool
6 Forest
6 Mountain
6 Plains
1 Acidic Sliver
1 Armor Sliver
1 Barbed Sliver
1 Basal Sliver
1 Blade Sliver
1 Bonesplitter Sliver
1 Brood Sliver
1 Clot Sliver
1 Crypt Sliver
1 Crystalline Sliver
1 Darkheart Sliver
1 Dementia Sliver
1 Essence Sliver
1 Firewake Sliver
1 Frenzy Sliver
1 Fungus Sliver
1 Fury Sliver
1 Gemhide Sliver
1 Ghostflame Sliver
1 Harmonic Sliver
1 Heart Sliver
1 Homing Sliver
1 Horned Sliver
1 Hunter Sliver
1 Lymph Sliver
1 Magma Sliver
1 Mesmeric Sliver
1 Metallic Sliver
1 Might Sliver
1 Mindwhip Sliver
1 Mnemonic Sliver
1 Muscle Sliver
1 Necrotic Sliver
1 Opaline Sliver
1 Plated Sliver
1 Psionic Sliver
1 Pulmonic Sliver
1 Quick Sliver
1 Quilled Sliver
1 Reflex Sliver
1 Root Sliver
1 Screeching Sliver
1 Sedge Sliver
1 Shifting Sliver
1 Sidewinder Sliver
1 Sinew Sliver
1 Sliver Legion
1 Sliver Overlord
1 Sliver Queen
1 Spectral Sliver
1 Spined Sliver
1 Spinneret Sliver
1 Spitting Sliver
1 Synapse Sliver
1 Synchronous Sliver
1 Talon Sliver
1 Telekinetic Sliver
1 Toxin Sliver
1 Two-Headed Sliver
1 Vampiric Sliver
1 Victual Sliver
1 Virulent Sliver
1 Ward Sliver
1 Watcher Sliver
1 Winged Sliver
1 Arcane Sanctum
1 Badlands
1 Bayou
1 Blood Crypt
1 Breeding Pool
1 Crumbling Necropolis
1 Godless Shrine
1 Hallowed Fountain
1 Jungle Shrine
1 Overgrown Tomb
1 Plateau
1 Sacred Foundry
1 Savage Lands
1 Savannah
1 Scrubland
1 Seaside Citadel
1 Steam Vents
1 Stomping Ground
1 Taiga
1 Temple Garden
1 Tropical Island
1 Tundra
1 Underground Sea
1 Volcanic Island
1 Watery Grave
1 Clifftop Retreat
1 Dragonskull Summit
1 Drowned Catacomb
1 Glacial Fortress
1 Hinterland Harbor
1 Isolated Chapel
1 Rootbound Crag
1 Sulfur Falls
1 Sunpetal Grove
1 Woodland Cemetery
I'm going to give you advice similar to what I gave to SorO: You need Wrath protection. Tsabo's Decree, Hallowed Burial, Death Cloud, Life's Finale, and good old Wrath of God ruin you. Also, an entirely creature-based deck is going to burn itself out very quickly. And I mean
VERY quickly. Once you are in topdeck mode, you are effectively out of the game entirely. Furthermore, several of the Slivers are not worth running.
Your manabase is also fairly weak (despite being mostly multicolor lands). The more effects you run that can tap for mana of any color, the more likely you are to be able to cast any spell in your hand.
Take a look at these decklists. Look at their Slivers and their noncreature spells.