Tainted characters are a new system introduced in Repentance that inherently changes how each of the main characters behaves in-game. To access Corpse, Isaac must defeat Mom in the Mausoleum, open the red door with both Key Pieces, and then defeat Mom's Heart which will spawn an entrance to Corpse. To access Mausoleum, Isaac must sacrifice two hearts worth of health at the end of Depths or Mines. To access Downpour, the player needs to use a key on the locked entrance at the end of the first chapter, To access Mines, you must bomb the exit of the second chapter (Caves/Catacombs). Once unlocked, each area has a unique entry requirement. The achievement A Secret Exit was added in Repentance, and it must be earned for the player to have a chance at finding these locations. However, these areas are not unlocked automatically upon downloading Repentance: they must be unlocked by defeating Hush three times. Each area is home to new enemies and new paths through the catacombs of Isaac's basement, as well as new bosses and unique encounters. The Binding Of Isaac: Repentance brings four new zones to the game – Mines, Downpour, Mausoleum, and Corpse.

Binding of isaac keeper