Duriel is the boss of Act Two, and must be defeated to advance to Act Three. He's found in the one true tomb of Tal Rasha, and reached by inserting the completed Horadric Staff into the orifice. Characters who descend through the tunnel opened by this event will encounter Duriel in a small, pit-like level where the demon's speed and charging ability can be put to merciless use. Duriel must be defeated to complete the [[Quests_Act_Two#Quest_Six:_The_Seven_Tombs|last quest in Act Two]], before moving on to Act Three is possible.