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Brittle Bones

AchievementAfterbirth+Unlock unknown

Achievement details

Achievement number: 396
Description: Unlocked a new item.
Requirement: Defeat The Lamb as The Forgotten

How do you unlock Brittle Bones?

In The Binding of Isaac, Brittle Bones is unlocked by earning the The Lamb completion mark as The Forgotten (Character).

Structured pathSource-backed requirements are mapped into trackable steps.

Unlocked a new item.

The Forgotten (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
- The Forgotten (Character)
  - The Forgotten (Achievement)
    How to unlock: It's complicated

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What unlocking Brittle Bones leads to

Source: bindingofisaacrebirth.wiki.gg

Imported 2026-09-13