i think ur theory is pretty on point, u got the most lore heavy and probably the definitive canon ending (if the author decides there is one). its very interesting how the skin walker mentions warmth, it would make sense for it to be setting up a chain of food, like the SCP. pretending to be a human, to lure more humans, like a cycle. it is very creepy. and interesting how the skin walker works. because it clearly didnt take Asters actual skin, as his body was still there, and it also most likely wouldnt have been able to kill a whole deer just for that moment. so maybe its a bit like that old minecraft mod, where once you kill a mob, you can transform into it whenever.