[[Image:Mon-izual.jpg|frame]]Izual is a fallen angel, imprisoned or corrupted into a demon. There's some nice fiction about him in the game quest info, and the Diablo II manual.
Izual is a hard monster to kill, but not an especially dangerous one. He doesn't hit very quickly or deal high damage, but he has a ton of hit points, and often takes new characters longer to kill than any other single monster on all of normal difficulty. Prior to v1.07 and the expansion, he was outrageously durable, and melee attackers often had to return to town for weapon repairs mid-battle.