Hmmm...Larloch.
See here :
http://forgottenreal...om/wiki/Larloch
Now, I believe this is going to be pretty difficult to build. Even with the PRC.
I would not make him a Mystic Theurg. He is obviously not a Priest.
I think the previously mentioned build is correct from Luminus. Pure Wizard, with Archmage (for the special spell-like abilities, which Archmage has, plus all the other goodies that Archmage adds), combined with Lich (because Larloch is a Lich of his own making).
I would give him all the spells, as Larloch has lived over 2000+ years, and his a surviving Netherese Arcanist-King.
To this, I would add a lot of items, including one that allows him to Summon 3 Demi-Liches. He should have the Arcane Fire feat as well. Also, he should have every Epic Spell (and his Lore should be as high as possible, allowing him to cast ALOT of them!). To that, I would add a Continguency Teleport: - that would allow him to escape when threatened below half hitpoints.
And yes, Larloch would dump on any NWN Wizard build. Or any build. In fact, Larloch would dump on any NWN Legendary Party builds. As he should - he is made to be a plot NPC IMHO, much like Elminster.