In the final Evil Route song, Decide, Isaac turns into a demon, giving him dark gray horns, black skin and red eyes, similar to his appearance with the item Brimstone.
In the final Good Route song, Innermost Apocalypse, Isaac takes form of his appearance from his boss counterpart, notably hovering with his wings. (Note that this is in the last part of the song.) In his old second song, Innocence Glitched, his appearance doesn't change for the most part, but his animations change his appearance to the other playable characters, the characters he changes into are as listed: He is also left-handed, but uses his right hand due to his mother being Christian, causing her to believe that being left-handed is sinful, as God would use his left hand to point people towards Hell. In this mod, his design is no different with his original counterpart, albeit the microphone and eyebrows. Isaac is a short, bald, naked crying child, with black eyes, white pupils, a round head, short body, a semicircle mouth with teeth, and no fingers or toes, it was confirmed that Isaac's mother shaved his hair off. He then jumps down without hesitation the moment his mother bursts through his door into the unknown depths below. He watches as she prepares to sacrifice him and struggles to find a way out before finding a trap door under the carpet. One day, she hears a voice from above, believing the hallucination is a higher being, likely Jesus or God, and she does what he asks, including the voice's final command to sacrifice her child, Isaac. Isaac is a 5 year old child who lives with his mother in a small house on a hill. Isaac is a character from the video game series The Binding of Isaac, created by Edmund McMillen. ― Isaac and his father discussing the ending to Isaac's story, The Binding of Isaac: Repentance Final Ending Here, how about we tell it a different way - maybe a happy ending?" “ Are you sure this is how you want this story to end, Isaac? You're the one writing it, it doesn't have to end this way.