Lost Soul is an unlockable familiar in The Binding of Isaac, added in the Repentance DLC.

Spawns a familiar that follows closely behind Isaac and dies in one hit, respawning at the start of the next floor.

If the familiar survives and is taken down to a new floor, it will rewards Isaac with one of the following:
• 3 Soul Hearts.
• 2 Eternal Hearts.
• 1 item from the Treasure Room or Angel Room item pool.

This page shows information as of the latest Repentance release.
To see latest up-to date information about this item for the new Repentance+ (Online Co-op) DLC, check this page instead.

Defeat Mother as The Lost.

Lost Soul can be found in the following item pools:

The following tags are applied to this item:

The following special synergies and interactions for Lost Soul have been documented.

* Note that not all possible synergies and interactions are listed here.

• Check out the item description on the external Isaac Wiki.