. . . is IMO a lovely piece of work, which shows off the game's combat engine to best advantage. It is doable (just about) by a level 11 party provided it has a couple of characters with the Turn Undead spell and missile weapons, and it is still a decent battle for a party of level about 30, although of course it is much easier for the higher-level party.
The start of the (long!) road that leads eventually to the place where you can promote your scholar to lich can be found in Thronheim, and your eventual destination will be pretty obvious when you find it. But you'll know you've been in a fight by the time you do the promotion, believe me!