User blog comment:Babysync/Dust/Aura link speculation/@comment-10678163-20130823114713

Wait, so Grim, (going on your theory), could be the animals who have had their auras taken from them so now want revenge/to protect other animals, hence why Pyrrha said that Grim are the only things without souls. While I don't think it's likely, it's a really interesting theory.