(SPOILERS?) I only saw ending 1 and 4 so far, but I'm wondering if David is actually just a psycopath because of everything he went through, shaping him to become a serial killer torturing victims and making them suffer like him, or if he really is a "vessel" and has something dark within him causing him to be that way. It seems to be more hinted at him simply having lost his mind thanks to the cult treating him in such an inhumane manner though...