Me again
So, my long running D&D campaign is just about coming to a close, and I finally need to stat up the final villain.
Brief campaign background[spoiler]
In a nutshell, several millennia ago a powerful Demi Lich attempted a ritual to ascend himself to Godhood. He "seduced" a (very) minor goddess of.. lets just say "pleasure", into spending the night with him, and she bore him six children. Due to a ritual on the Lich's part each of those six children possessed a larger than usual amount of divine essence, and the Demi Lich planned an elaborate ritual to use that essence for himself.
Each of his children, after they grew up recruited a right-hand man (or dog in one case), and the plan was for each Lich's Child to pass their divine essence into their second, and then kill them. The Demi Lich would then use the freed essence to ascend to Godhood, then raise his Children to be his heralds (and some of them would no doubt raise their seconds in turn). However, during the ritual one or more of the seconds panicked, which led to them all rebelling at the last moment.
The ritual went awry, the entire kingdom was torn from Faerun and thrown into a bubble plane in the Abyss. The Lich was trapped in his Phylactery and the seconds were all killed. However, in spite of their change of heart they were denied entry into the upper planes until they set things right and the plane was returned to its proper place.
The only way to do this is for either the Demi Lich to ascend, or for the ritual to be modified to destroy him. And so began a cycle where both the heroes and the Lich's Children are reborn every few decades to clash until one side wins.
Due to the precise situation and ritual needed to pull this off one way or the other, thus far has only been several thousand years of stalemate as one side wipes out the other without performing the ritual (or most of the time even getting to it).
However (naturally) this time the PCs may actually succeed...
[/spoiler]
The plan for the Demi Lich* The Demi Lich is be a lvl 20-30 triple-Gestalt (Favoured Soul/Sorcerer/Unarmed Swordsage, with Geomancer taking up ten of the Sorcerer levels), no Epic spells, unsure on 10th level or above spell slots.
* The Demi Lich cannot use his soul-draining ability since he needs the PCs souls to do the ritual in the first place
* The Demi Lich is little more than a disembodied spirit trapped in his phylactery until the ritual starts, so while he has plenty of mental prep and knowledge about the PCs, he can't actually prepare anything beforehand (though he's got a full swag of magic items)
* Depending on exactly what the PCs do during the final ritual, individuals may be immune to many of his Demi Lich abilities (including being able to bypass his magic immunity, and insight bonuses to AC etc)
* The Demi Lich will be taking on a semi-corporeal fully bodied form seemingly carved from crystalised negative energy so that he actually has a full body to fight with. This will negate his size bonus to AC but allow him to use TWF etc.
* He will have backup in the form of the souls of his children, but how useful they are will depend on what the PCs do (they will be 20th level Gestalts with no gear, and may or may not be able to affect the PCs)
What I'm mostly looking for is suggestions for what abilities will synergise well with what is effectively going to be a "Magic Knight" style character, equally at home blasting from a distance or wading into melee. Obviously things like Divine Power (and perfect TWF) & Arcane Strike will be needed, as well as Arcane Spellsurge for casting a free spell every round, but beyond that I've never really used a high-level character who mixes melee & casting, nor have I used a high-level Swordsage (especially not one with access to huge gobs of magic) so if anyone can suggest feats/maneuvers/spells that would be viable for such a character, it would be very much appreciated
Also, thoughts on what spells I should make sure he has Spell Immunity for would also be very handy.