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King Baby

AchievementAfterbirth+Unlock unknown

Achievement details

Achievement number: 286
Description: Unlocked a new co-player baby.
Requirement: Defeat Delirium as ???

How do you unlock King Baby?

In The Binding of Isaac, King Baby is unlocked by earning the Delirium completion mark as ??? (Character).

Structured pathSource-backed requirements are mapped into trackable steps.

Unlocked a new co-player baby.

??? (Character) → Delirium (normal)
1. Defeat Hush to unlock The Void. source
2. A Void portal can appear after a major boss; defeating Hush guarantees one. source
3. Defeat Delirium, the main boss of The Void. source
- ??? (Character)
  - ??? (Achievement)

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What unlocking King Baby leads to

Source: bindingofisaacrebirth.wiki.gg

Imported 2026-09-13