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Mystery Sack

ItemRebirthLocked

familiarGame ID 271★★★★

How do you unlock Mystery Sack?

In The Binding of Isaac, Mystery Sack is unlocked by earning the The Lamb completion mark as Eden (Character).

Structured pathSource-backed requirements are mapped into trackable steps.

Spawns a familiar that drops a Heart, coin, Bomb, or Key every 5-6 rooms.

Mystery Sack (Achievement)
- Eden (Character) → The Lamb (normal)
  1. Defeat Satan 5 times to unlock The Negative. source
  2. The Negative is a guaranteed drop from Mom; take it, then defeat Satan in Sheol and touch the chest to enter Dark Room. source
  3. Find and defeat The Lamb in Dark Room. source
  - Eden (Character)

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What unlocking Mystery Sack leads to

Nothing depends on this yet.

Source: bindingofisaacrebirth.wiki.gg

Imported 2026-09-13