Fridge / The Binding of Isaac: Antibirth

• Why can the Corpse only be accessed by using the Knife Pieces to kill Mom's Heart early? Well, let's think. When he has the chance, he goes straight for the heart before she's able to get away. This could imply on the normal path, she has time to put her heart in a secure place in the Womb/Utero while Isaac needs to fight through multiple enemies and rooms first. But in Mausoleum, she has no such opportunity. Therefore, killing her heart early leads him to her Corpse, because he effectively stopped her from escaping after the first defeat. No wonder she has different moves in Mausoleum - she has an Oh, Crap! moment and realizes he has something other than his tears to definitely destroy her, so she changes up in a desperate attempt to stop him. Hell, maybe the entire reason he goes on the alt path is because instead of just trying to survive, he genuinely wants to fight back against her and deliberately seeks out something to put him on even footing with her. Of course, this all relies on the symbolism of the Knife Pieces...
  • As an aside, why can't you access the Corpse on the regular path? Because by the time Isaac realizes he has to kill her, it's too late, she's already retreated into her Womb. And being a child, perhaps he doesn't think just using Mom's Knife or the Sacrificial Knife will work. For him, Isaac may think he needs something he puts together on his own to definitely kill her. This, for the alt path, it starts with her wielding a knife of her own, and it ends with him wielding a knife of his own.
• Regarding the Heretic, there might be another angle in why it killed off its followers when it was summoned. If you look back at the Forsaken fight, it puts its bony appendneges up to its face like its scared or in pain. After all, it’s first form had an bony interior but now it’s just bones. Therefore, after suffering a brutal defeat where it’s skin got ripped off, the Forsaken fights Isaac, loses and perhaps it got relief from the pain it was in. Then the Fanatics come in and revive him again but as the Heretic and pissed at being revived and relieved of its possible pain, it lashes out at everything it sees starting with the ones who summoned it.