Question: how to unlock binding of isaac characters?
Answer: Isaac : Unlocked by default. Magdalene : Have seven or more Heart-Containers at once. Cain : Have 55 or more cents/pennys at once. Judas : Defeat Satan. ??? aka Blue Baby : Defeat Mom's Heart 10 times. Eve : Beat two floors in a row without picking up any hearts. Samson : Beat two floors in a row without taking any damage.