Diablo/Zhar, the Mad

At catacumbs level 8, find Zhar, the mad sorcerer that thinks he's powerful. Talk with him and he will handle you a random spellbook. However, he will warn you to not touch the bookcase, since the wisdom contained there is only him. (But he is not our boss! He can't tell us what to do!).

To make him pissed, grab the book on the bookcase and he will start attacking you. He is kinda tough but some blows may kill him.

When dead, he will drop a random item that can be unique, magic or even normal.