Red Key is an unlockable active item in The Binding of Isaac, added in the Repentance DLC.

While heldIndicates walls that can create a Red Room with a red outline.

On useCreates a Red Room when used next to one of the red outlines on walls.

Red Rooms are most commonly same as normal rooms, but with a 10% chance to be any type of special room instead. It can create these types of rooms:
• Angel Room
• Arcade
• Bedroom
• Curse Room
• Devil Room
• Dice Room
• Library
• Mini-Boss Room
• Planetarium
• Sacrifice Room
• Secret Room
• Shop
• Super Secret Room
• Treasure Room
• Vault

Rooms created by Red Key will always be 1x1 rooms with doors available on all sides.

If a door leads Isaac outside of the 13x13 playable area of the floor, it will take Isaac to the I AM ERROR room.

Since Secret Rooms cannot be overwritten by Red Key, the lack of an red outline can be used as an indicator that a Secret Room is possibly located behind the wall.

If a created Red Room is adjacent to the Ultra Secret Room, its entrance will immediately open along with a jingle sound.

Has no effect in Greed Mode and cannot normally be obtained there.

Can be used to open the hidden closet door in the Home level that unlocks the Tainted version for each character. If the character has already been unlocked, this room will contain Inner Child, or a Shopkeeper if not unlocked.

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

Open Mom's Chest in the Home level.

Red Key can be found in the following item pools:

The following tags are applied to this item:

The following special synergies and interactions for Red Key have been documented.

* Note that not all possible synergies and interactions are listed here.

Below is the Internal Item Description as shown in-game.
Note that some stat changes are not displayed here. Please see the main description for the full effects.

Red Key

• Opens nearby doors to mysterious hidden red rooms
• While held, the outlines of these hidden doors can be seen on certain walls
• Abyss: x1 locust 1.5x Isaac's damage
• Book of Virtues: x1 middle wisp - 1.5 hp - 3 damage
• Book of Virtues: Chance to open red rooms

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