Lost Soul

ItemRepentanceLocked

familiarGame ID 612★★★★

How do you unlock Lost Soul?

In The Binding of Isaac, Lost Soul is unlocked by earning the Mother completion mark as The Lost (Character).

Structured pathSource-backed requirements are mapped into trackable steps.

Creates a ghostly familiar that closely follows behind Isaac. It dies in one hit, but respawns at the start of the next floor. Each time it survives until the next floor, it rewards Isaac with Soul Hearts, Eternal Hearts, or an Item.

See the full unlock path for Lost Soul — 9 steps

Lost Soul (Achievement)
- The Lost (Character) → Mother (normal)
  1. Defeat Hush 3 times to unlock A Secret Exit. source
  2. After A Secret Exit is unlocked, a locked door to Downpour appears after completing Basement/Cellar/Burning Basement I or II. source
  3. Collect Knife Piece 1 in Downpour/Dross II. source
  4. Collect Knife Piece 2 in Mines/Ashpit II. source
  5. After defeating Mom in Mausoleum/Gehenna II, stab the flesh door that appears with the knife familiar to open it. source
  6. Defeat the Mausoleum version of Mom's Heart behind the flesh door, then reach Corpse II and defeat Mother. source
  - The Lost (Character)

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What unlocking Lost Soul leads to

Nothing depends on this yet.

Source: bindingofisaacrebirth.wiki.gg

Imported 2026-09-13