Isaac Moriah from The Binding of Isaac canonically is developing Dissociative Identity Disorder at the time the game takes place, as confirmed by an AMA done on twitter by the creator.
This is also shown in-game with both the gameplay mechanic of choosing characters being very easily corelated to Isaac's religious-zealoutous upbringing that would most likely create alters based off of biblical figures and characters. Multiple endings also show that Isaac percieves a "seperated" bad/evil version of himself to cope with his abuse by compartmentalizing it, and this is shown in his drawings as well. There's probably more that can be analyzed from this but it is personally a big triggering to look into too hard for us.
(Isaac we love you.)
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