What about putting it somewhere in the Attnam Underground, maybe into a glass coffin?
There already is a coffin at the bottom, if I recall correctly, only it looks as a bookshelf.
It could be a special room for AU, as it has none.
Also, what about making that coffin at the bottom of AU actually spawn the Zombie of Khaz-zadm? Shouldn't it have been a boss for this dungeon? Now only the warning when you open the coffin is shown, not the zombie spawned.