Bone Baby
AchievementAfterbirth+Unlock unknown
Achievement details
- Achievement number
- 402
- Description
- Unlocked a new co-player baby.
- Requirement
- Earn all Hard mode Completion Marks as The Forgotten
How do you unlock Bone Baby?
In The Binding of Isaac, Bone Baby is unlocked by earning every hard-mode completion mark as The Forgotten (Character).
Structured pathSource-backed requirements are mapped into trackable steps.
Unlocked a new co-player baby.
See the full unlock path for Bone Baby — 14 steps- All of
- Defeat Satan 5 times to unlock The Negative. source
- The Negative is a guaranteed drop from Mom; take it, then defeat Satan in Sheol and touch the chest to enter Dark Room. source
- Find and defeat The Lamb in Dark Room. source
- ??? or The Lamb must be defeated once for the Golden Gate to spawn. source
- Open the Golden Gate by combining Key Piece 1 and Key Piece 2 into the Golden Key, or by using Dad's Key or another gate-opening effect. source
- Reach the starting room of Chest or Dark Room, pass through the Golden Gate, and defeat Mega Satan. source
- Defeat Mom's Heart for the 10th time to unlock Blue Womb. source
- Defeat Mom's Heart or It Lives! within 30 minutes and enter the door to Blue Womb. source
- Defeat Hush in Blue Womb. source
- Defeat Hush to unlock The Void. source
- A Void portal can appear after a major boss; defeating Hush guarantees one. source
- Defeat Delirium, the main boss of The Void. source
- Defeat Hush 3 times to unlock A Secret Exit. source
- After A Secret Exit is unlocked, a locked door to Downpour appears after completing Basement/Cellar/Burning Basement I or II. source
- Collect Knife Piece 1 in Downpour/Dross II. source
- Collect Knife Piece 2 in Mines/Ashpit II. source
- After defeating Mom in Mausoleum/Gehenna II, stab the flesh door that appears with the knife familiar to open it. source
- Defeat the Mausoleum version of Mom's Heart behind the flesh door, then reach Corpse II and defeat Mother. source
- A Strange Door is unlocked by beating Mother for the first time. source
- Take The Polaroid or The Negative after Mom, escape the boss room, then use it to open A Strange Door. source
- Find Dad's Note, complete the Ascent to Home, then defeat Dogma, the Ultra Harbingers, and The Beast. source
What unlocking Bone Baby leads to
Source: bindingofisaacrebirth.wiki.gg
Imported 2026-09-13