This character is secret and does not appear in the character selection menu
He has no hearts, he dies with 1 hit, has flight and gets deals with the devil for free (the deal does not kill and does not reduce anything)
First, we must die from a crybaby-kamikaze at the basement level for Isaac, Then we die from our own bomb for Magdalena at the level of the caves, we die as a Judas from our mother (not from the monsters that she summons) and the very last step is to die for Azazel from Satan
If you play Afterbirth it’s much easier.
Die for any character with missing poster (do not confuse with missing page)
Note: in Rebirth with the Missing poster, we open the puzzle pieces but it is useless