Mystery Sack - The Binding of Isaac

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Mystery Sack is an unlockable familiar in The Binding of Isaac.

Spawns a familiar that follows Isaac and drops a heart, coin, bomb or key every 5 or 6 rooms alternatingly.

Pickups can be of any variant.

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.

Defeat The Lamb as Eden.

Mystery Sack can be found in the following item pools:

Name	Weight
Treasure Room	1.0/1.0
Secret Room	1.0/1.0
Beggar	1.0/1.0
Greed Treasure Room	1.0/1.0
Greed Secret Room	1.0/1.0

The following tags are applied to this item:

Id	Description
summonable	Can be summoned via Lemegeton.
offensive	Can appear for Tainted Lost.

The following special synergies and interactions for Mystery Sack have been documented.

Mod	Item	Synergy
---	BFFS!	The familiar drops pickups every 4 or 5 rooms.

* 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.

Mystery Sack

• Familiar that drops a random pickup every 5-6 rooms
• Abyss: x1 locust 1x Isaac's damage