Undefined
ItemRebirthLocked
activeGame ID 324★★★★
How do you unlock Undefined?
In The Binding of Isaac, Undefined is unlocked by earning the Boss Rush completion mark as Eden (Character).
Structured pathSource-backed requirements are mapped into trackable steps.
Teleports Isaac to the Secret Room, Super Secret Room, Treasure Room, or I AM ERROR.
What unlocking Undefined leads to
Nothing depends on this yet.
Source: bindingofisaacrebirth.wiki.gg
Imported 2026-09-13