- Whenever Isaac clears a room, has a chance to open a neighboring Red Room.
- This effect can occur while Isaac is inside a Red Room, but the chance is smaller.
- It's possible to increase the chance of a Red Room unlocking if multiple Crystal Keys are held, e.g. from absorbing using Smelter, holding Mom's Box, having a golden Crystal Key, or other methods. The chance for a Red Room door to unlock depends on the number of Crystal Keys held and if the room cleared is normal or Red.
|Crystal Key Count||Normal Room||Red room|
- Each cleared wave of a Challenge Room has a chance to generate an adjacent Red Room.
- Rooms that are re-fought using the D7 have a chance to generate additional Red Rooms.
- Doors do not have to open to an actual valid Red Room, and can lead outside the map and into an I AM ERROR Room.
|Cards and Runes|
|Tainted Lost Unlocks|
|The Binding of Isaac: Rebirth|
|Achievements||Attributes||Bosses||Cards and Runes||Challenges||Chapters|