The Rift

Unlock the Rift, Act 2's secret area. After clearing the Core, Pyrophina appears as a house boss. Defeat her to obtain the Scalding Orb, then take it through a run of the Moon. When you reach the Man in the Moon boss, allow him to devour the cat holding the Orb. This sacrifice triggers the black obelisk on the Moon, opening the path to the Rift. The Rift contains some of the most challenging encounters in Act 2 and connects to the endgame secret content.