Critique this gish.

[Amechra]

This Gish is created with one piece of houseruling; namely, that you can grab Prestigous Versions of those alternate Paladins that are devoted to a different alignment.

High Lord Corrupter of Mystra

Illumian NE Cleric 1/Rogue 4/Assassin 4/Prestige Corrupter (The NE variant of the Paladin) 1/Unseen Seer 10

Deity: Mystra
Domains: Trickery, Knowledge
ACFs: None.

2 Flaws: Any

Feats:
Flaw: Heretic of the Faith
Flaw: Extend Spell
1st: Persist Spell
3rd: Craven
6th: Alternate Source Spell
9th: Mounted Combat
12th: Sword of the Arcane Order
15th: Versatile Spellcaster
18th: Practiced Spellcaster (Assassin)

My sigils are the pair that grant you 2/day DMM.

Pros: Death Attack, 2/day DMM Persist, 4th level Assassin, Paladin, and Wizard Spells (5th level max for Wizard Spells), Turn Undead, CL 23 for Divination spells,CL 16 for non-Divinations. Instant Death Attack, Sneak Attack 8d6+20 unbuffed, 15d6+20 Buffed.

Cons: You tell me; it will be more honest that way.

[juton]

I think Unseen Seer is Arcane only, so that will have to change. Why 4 levels of Rogue, if you want sneak attack just take 1 level, or 3 if you are really keen on it, remember to not lose unnecessary caster levels. Do you really need Assassin at all in this build? You could probably emulate everything you need to with a properly set up cleric build.

Right now, if you take your class levels in the order listed you will not be pulling your weight around levels 5-12, which are the parts of the game that matter most. I think you'd be better off going Spellthief 1/Wizard 4/Unseen Seer X/Arcane Trickster Y, that's a more generic build. Is there something specific you want to accomplish with your build?

[Endarire]

Were you going for a Rogue/Caster build?  The more traditional gish is Warrior/Caster.

[gorfnad]

Don't you need 4 levels of Paladin in order to qualify for Sword of the Arcane Order?

If you want a sneaky Mystra based divine caster how about:
Rogue 3/ Cleric 3/ Prestige Paladin 4/ Divine Trickster 10
This lets you not only have the Sword of the Arcane Order feat but also the Initiate of Mystra feat as well.

[kurashu]

If you want a sneaky Mystra based divine caster how about:
Rogue 3/Cloistered Cleric 3/ Prestige Paladin 4/ Divine Trickster 10

Fix'd.

[gorfnad]

If you want a sneaky Mystra based divine caster how about:
Rogue 3/Cloistered Cleric 3/ Prestige Paladin 4/ Divine Trickster 10

Fix'd.

Not quite, Prestige Paladin requires BAB +4. Going cloistered would only net BAB +3.

Although going Rogue 3/ Cloistered Cleric 4/ Prestige Paladin 4/ Divine Trickster 9 might work. With the feat Sacred Outlaw (Dragon #357) you make up for the sneak attack you would have normally gained from the last level of Divine Trickster.

[kurashu]

D'oh. Honestly, though, if you want the wizard spell list on a divine caster, just take archivist instead. They automatically draw spells from all divine spells. Between Divine Bard, Divine Magician and Southern Magic/Alternate Spell Source you're all set and it's less eyebrow raising than SotAO on a Prestige Paladin.

Try going: Alternate Archivist and Rogue levels for the first 7 levels (Archivist 4/Rogue 3). Then Sacred Exorcist 1/Divine Trickster 10

I would say finish it off with levels in Sacred Exorcist, Seeker of the Misty Isle (Travel Domain at 1st level, but you have to be an elf/half-elf), or more archivist. There's also shadowbane stalker in Complete Adventurer.

EDIT: I'd also like to draw your attention to Player's Handbook II, page 114-115. A spell called Hunter's Eye. Gain +1d6 sneak attack per 3 caster levels. It only lasts for 1 round but it's a swift action to cast. Just straight from this build you'd get an extra 5d6 of Sneak Attack, Practiced Spellcaster boosts that to +6d6. And that's not even attempting to blow CL through the roof.

So you're looking at +13d6 of Sneak Attack before any other CL boosters. Not to mention there are all sorts of Ranger spells that would help with sneakiness as well.

[Amechra]

There is an Arcane Class; what do you think Assassin is?

Prestige Paladin advances Assassin; that's what Alternate Source Spell is for.

I thought the general consensus on Prestige Paladin+Sword of the Arcane Order is that it would be 4 levels of the class your advancing counts as Paladin 4.

[PhaedrusXY]

There is an Arcane Class; what do you think Assassin is?

Prestige Paladin advances Assassin; that's what Alternate Source Spell is for.

I thought the general consensus on Prestige Paladin+Sword of the Arcane Order is that it would be 4 levels of the class your advancing counts as Paladin 4.

You're all out in house rule territory anyway, but I'd certainly say no to that. 4 levels of paladin is 4 levels of paladin. You can't qualify by advancing your spellcasting anymore than you could with a monk3/paladin 1 and the feat that lets you stack their levels.

[Amechra]

Alright, everyone ignore this from now on.

I will, from now on, make extra sure of everything before I post.