Red Redemption is an unlockable challenge in The Binding of Isaac, added in the Repentance DLC.

This page shows the latest information as of the new Repentance+ (Online Co-op) DLC.
To see information about this challenge for the previous Repentance version, check this page instead.

Dad's Key

Note: this list does not include characters' default starting items.

The starting room has no rooms connected to it. Rooms spawn in clusters around the map must be found via Red Key.
Red Key has infinite uses but after 20 uses Dark Esau will spawn.
Each subsequent 5 uses will spawn another Dark Esau if Tainted Jacob has not turned into his Lost form.
I AM ERROR rooms cannot be accessed via Red Key.
Every floor generates as a Curse of the Labyrinth! floor, having 1 Shop, 2 Treasure Rooms, and 2 Boss Rooms.
The 4th floor has only 1 Boss Room.
Any room may be from any floor of the current chapter.

The following is unlocked for completing the Red Redemption challenge: IX - The Hermit?

Open the hidden closet on the Home floor as Jacob and Esau.

• Check out the challenge description on the external Isaac Wiki.