His mother, fueled with the desire to serve her God, was bearing down on Isaac. The following is a transcript of the dialogue from the epilogue. Isaac quickly becomes shocked at the sight. Seconds later, the door to Isaac's room bursts open, and Mom appears again with a knife in her hand. Unfortunately, this turns out to be just a story that Isaac has written.
In a drawn sequence similar to that of the Title Sequence, Isaac's mother closes in, trapping Isaac in a corner, preparing to kill him, when The Bible drops down from above and kills her.
They can be unlocked by killing the boss at the end of chapters 3-6. There are 16 endings in Rebirth, with 2 more added in Afterbirth, 2 added in Afterbirth+ and another 2 added in Repentance. They are all different and some depend on the player's route through the game. Endings are cutscenes at the end of each completed run.