Building a rogue from a Psion

[RealMarkP]

I will be starting a campaign in the Warhammer 40K universe. The DM spent a considerable amount of time converting a GRUPS WH40K rulebook and modifying the d20 Modern rules to fit into it. Psionics is the bread and butter of the game and yours truly will be taking part in that. We are using a point buy system for EVERYTHING (feats, power points, skills, etc), where you exchange XP points for these things. He has also limited us to only the Psion abilities and powers.

So, given that I basically have a Psion and core non-psionic classes what are my options for making a rogue-like character with psionic powers? What kind of feats/powers should I invest in (Core books, plus complete psionic and expanded psionic books)?

As a side note, I'm in the process of asking if the Psychic Rogue variant is allowed. EDIT: This class is allowed.

[phaedrusxy]

Psychic Rogue kind of sucks. Just Rogue 1/Psion X can work fine. If you don't actually need the trapfinding stuff (and honestly, it's over rated), Ranger 1/Psion 6/Slayer 10/Psion +X works well, also.

[RealMarkP]

Psychic Rogue kind of sucks. Just Rogue 1/Psion X can work fine. If you don't actually need the trapfinding stuff (and honestly, it's over rated), Ranger 1/Psion 6/Slayer 10/Psion +X works well, also.

I was hoping to take advantage of the Sneak attack abilities (as much for combat as backstory reasons). Would your build allow for that?

I'm also allowed one Flaw, which I will take.

[phaedrusxy]

Psychic Rogue kind of sucks. Just Rogue 1/Psion X can work fine. If you don't actually need the trapfinding stuff (and honestly, it's over rated), Ranger 1/Psion 6/Slayer 10/Psion +X works well, also.

I was hoping to take advantage of the Sneak attack abilities (as much for combat as backstory reasons). Would your build allow for that?

No, but it's not like rogues have a monopoly on stabbing things really hard.

If you go with the first idea (rogue 1/psion X), you can take the Craven feat and also pick up Martial Stance (Assassin's Stance), and then buy some of the weapons that boost sneak attack, but that's burning a lot of resources for a relatively small boost in damage. Unfortunately, there isn't really a good psion prestige class that advances sneak attack that I know of. Since you're homebrewing anyway, I'd suggest adapting the Unseen Seer. It isn't that difficult. I think I even have an adaptation that I used for a character laying around somewhere, if you're interested.

[Unbeliever]

A sort of funky idea might be grabbing the Avenging Executioner or whatever it's called -- a 5 level class that advances sneak attack and that gives you the ability to sneak attack people you frighten.  There is Primal Fear, a nice swift action fear power, not to mention other fear tricks, which would give you a lot of sneak attack options.  You manifesting will take a hit, but Psions (and especially Ardents) deal with that reasonably well.

Adapting Unseen Seer or similar Rogue/Caster hybrid classes is a good idea, too.  That's one of the things with psionics, there's not a ton of system support for it. 

[sirpercival]

If you do the fear build, get a psi adaptation of the Dread Witch so you can affect fear-immune folk.

[Cyclone Joker]

It depends on the type of rogue you want to make. If social, Tempest Stormwind recently made a gorgeous build on the WotC forum. If dungeon-crawling, Slayer is really all you need, the right power selection will solve most of the problems for you. For DPR, the psion has the rogue beat, but, for precision damage, beyond just going Martial Stance:Assassin's Stance at level 12? I got nothing. For damage, an egotist, or just any psion with the right powers should outdo any rogue.

How are you handling Perils? And might I point you at Dark Heresy. It sounds like it's got everything your DM wants, but better.