Hmm... I would go thief for purist. His slightly better stats make up for the lack of preps, although I could see an argument for transmuter too. That's more of a personal choice. Assassin, Priest, Crusader, and Half-Dragon are also good choices. You should definitely NOT do Monk (relies on finding early glyphs for damage), Sorcerer (relies on finding early glyphs for leveling, especially BURNDAYRAZ), Bloodmage (that mana penalty without preps HURTS), Vampire (he needs either Binlor or Titan Guitar for this place, or he will have no blood cows). Alternatively, if you want a less luck reliant but much more difficult purist run, go gorgon so you don't have to worry about walls.
I speak chaos.