I agree that the Crawler is a void being, and I am leaning into believing that he may be a part of the shadow court(but thats just my opinion). The reason for that is I noticed while you were crossing the desert, after leaving Walter, you see the crawler mimicing Walter as you continue and he keeps taunting the hero, then suddenly you see him walking around talking to himself and he seems to speak of himself in third person and seems to be telling his story(at least thats what I am guessing) and tells about how the *3* of them were forced into the darkness until they lost all light and became dark and cold, or something of the like. I can't remember the exact specifics, but I would like to think its telling the origin of the shadow court? 3, darkness, 3 shadows? I dunno I'm just throwing that up there.