Ok, so White Sand is the only part of the Cosmere I haven't read yet, so Trell the character and Autonomy are not familiar to me. But I'm still leaning on the Trell/Odium connection. The Coppermind confirms that Odium moves throughout the cosmere, and there is a discussion where Brandon discusses that Odium is aware of and plotting against Harmony:
Also, I feel like there is a perpedicularity in the Seran Ranges on Scadrial. If you read one of the broadsheet entries in either Shadows of Self or Bands of Mourning, the contributor mentions coming across a lake described very much like the one in Elantris. This is the same broadsheet entry that depicts the red and black masks of the Mawlish (which to me seem very much like stylized representations of the Parshendi). We know that Odium is having the voidspren patrolling the perpedicularities on Roshar. So here's part of what I've come up with: Odium may not be directly on Scadrial, but his Voidbringers are, and the Mawlish at some point in their history have encountered them, or other Parshendi, and it has influenced their masks. Or the broadsheet contributor saw a Voidbringer. On Roshar, the representations of the Shards in the Physical are the spren; on Scadrial, they are mists that condense into metals. So if you have Voidbringers (and their voidspren) that have worldhopped onto Scadrial through a perpendicularity that Odium controls, you could make a Hemalurgic spike from the voidspren once on Scadrial. And then you spike a kandra, and boom, Void-kandra that Odium has a direct link to on Scadrial. So there's the glowing-eyed being that kills Edwarn, which he even remarks upon as Trell's kandras.
But I also feel like the humans that fled to Roshar came from Scadrial, since the last trilogy of Mistborn is supposed to be space-agey, and Odium wants to destroy Harmony. Is there anywhere where Brandon has said where Mistborn and Stormlight are occurring at the same time? So perhaps Odium hasn't been tied down in the Rosharan system yet, and the Desolations haven't even started. Maybe the Parshendi are just living peacefully with Honor and Cultivation, Odium is floating through the cosmere and decides to destroy Harmony, attaches to the humans that then flee Scadrial, end up in Roshar, and then the Desolations start. I don't know how this timeline fits with anything Brandon has said.
