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Duality item
Duality is an unlockable passive item in The Binding of Isaac, added in the Afterbirth+ DLC.
Description
Causes both a Devil and Angel Room to spawn whenever one would spawn normally after defeating a boss.
Only one of the rooms can be entered, causing the other one to disappear.
Both rooms will spawn, even if a Devil Deal has been taken before.
Sometimes only one room will spawn if the boss room does not have enough space for both.
Note
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.
How to unlock?
Defeat Ultra Greedier as 
Lilith.
Item pools
Duality can be found in the following item pools:
| Name | Weight |
|---|---|
| Devil Room |
1.0/1.0
|
| Angel Room |
1.0/1.0
|
Tags
The following tags are applied to this item:
| Id | Description |
|---|---|
| summonable | Can be summoned via  Lemegeton. |
| offensive | Can appear for  Tainted Lost. |
| lazarussharedglobal | Passive effects (except direct stat changes) are shared between  Tainted Lazarus' forms. |
Internal item description
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.
Duality
• Whenever an angel room or devil room entrance appears after a boss, the other also appears
• Entering 1 of the 2 doors causes the other to disappear
• Abyss: x1 holy Brimstone locust .75x Isaac's damage
External links
- Check out the item description on the external Isaac Wiki.
Ghost Pepper 
Euthanasia 
Camo Undies 
Eucharist 
Sack of Sacks 
Greed's Gullet