The events in the Antibirth mod from The Binding of Isaac aren't canon in the sense that it was just a mod at that specific point in time.
But it all changed in 2018, when Edmund McMillen, creator of the original game, approached the team behind the mod to actually implement most of the items and stories from it to the full game, and the result from that is the *Repentance* DLC.
Such a shame that the official, original music from the DLC can't beat the soundtrack from Antibirth.
