Part of me still thinks that Trell is Odium. It seems possible that he could get driven away from Roshar and attempt to attack Scadrial. It does not seem like a coincidence that Hoid asks Harmony for help in Oathbringer letters, then shows up later in Mistborn Era 2 subtly helping Wax fight the Set (possibly just tools of Odium).
However, there is still strong evidence for Trell being Autonomy. But given this, I still think that Autonomy and Odium are related in some way. They could be allied in some capacity.
I am convinced that Harmony helps Hoid in some way that prompts Autonomy, Odium, or both to attack Scadrial. I would think that intervening with a conflict on another system would be frowned upon by Autonomy and possibly be received as a threat (especially since Harmony is essentially as powerful as two shards).
