Spells & Class features to steal - Help

[generalcharon]

Hello all!
Minor conundrum for you.
I have statted a villain, final challenge for a lvl 20 gestalt campaign.
He's a large sized outsider, epic level, Swordsage//Warblade but also with the ability, thanks to his environment, to duplicate/mimic spells and class features.

So I'm trying to come up with a list of handy stuff for him to use/duplicate. He's primarily a melee guy, adept at both TWF & THF. He'll be able to use one spell per round as a free action (arcane, divine, doesn't matter), as well as be able to mimic a class feature (probably only one at a time) from any base class, and any PrC that's not too esoteric.

Any thoughts on some standout options? He'll be facing anything from six to ten PCs and their animal companions, and he'll have four big arse CR 23 Cerberus-like hellhounds on his side.

[Optimator]

Mettle. Arcane Resistance. Furious COunterstrike and the damage pool.

[Thiyr]

the Factotum's Cunning Brillinace. Insert Xzibit here.

More seriously, opening up with the Dread Necro's fear aura could be nice, and (were it not for the pesky line i just noticed saying non-humanoids don't get the class feature) it could be outright mean to use the same class's Lich Transformation to temporarily get undead immunities, if the party at all relies on say, precision damage.

Confuse the party with the Healer's Unicorn Companion ability. Consider summmoning the alternative companions if the amusement of that isn't worth its less effectiveness.

If the fear aura worked, double up with Mass Staredown from the Samurai. Find another source of fear to get it up to panicked. Tee hee.

The Swashbuckler's Lucky ability may be useful, though that's a tad too reactionary for my tastes.

Spirit Shaman's Favored of the Spirits may be a good one to toss in as a way to do the "real final ultimate form" bit.

If you don't mind messing a bit with implementation, getting the meldshaping of a totemist/incarnate may not be a bad thing either. Suddenly growing two more arms and using Girallon Windmill Fleshrip would be a nifty trick to have indeed.