So the whole origin of humans on Roshar still doesn't exactly add up to me.
I can totally buy that the dawnsigners (listeners? parshendi? whatever,) were invaded, desolated, and subjugated. That's totally in line with what I would expect.
However there are plenty of other items with don't seem to mesh with that narrative.
What was the nature of humanity upon their arrival on Roshar?
All we seem to know is that humans were fleeing some cataclysm on their former world. Were these good humans who were fleeing not only the destruction of their world but also the evils of their own kind (a la Númenóreans)? Were they instead servants of Odium, who made a similar deal to the kind Taravangian made at the end of Oathbringer? Or was it some combination?
We also don't know if all the humans represented on Roshar during the course of the series were following Odium. It seems like there are ten or eleven vastly ethnically distinct peoples: the Aimians, the Alethi, the Iriali, the Makabaki, the Natan, the Parshendi, the Reshi, the Shin, the Thaylen, and the Vedens, Within these ethnic groups there are some further divisions due to intermarrying: the mixing of Alethi hair, the Herdazian fingernails, Horneater red hair and jaws, etc.
This makes me wonder if there were actually humans from different worlds who were following onto Roshar. Or perhaps if there were some humans present on Roshar before Odium and Co. arrived. The closest hint we have to what the original refugees/invaders look like is the heralds themselves. This doesn't give us too much information as we've only seen four of the ten: Ash, Jezrian, Nale, and Taln. Of the four, Jezrian seems the closest to being a proto-Alethi. He is described as having skin a shade too dark and features which don't quite match. His daughter Ash looks more Makabaki, with an even darker skin tone. However, she is noted to have Shin eyes, that is, eyes without an epicanthic fold. We don't know much about what Nale and Taln look like other than they have dark, Makabaki-like skin and large builds. Nale also has a silver birthmark on his cheek - I don't know what this implies.
It also seems that there are spren who match certain kinds of humans more closely than than others. Reachers are described as being shorter, stockier, and having Shin eyes. We can assume that Honor spren have eyes with the epicanthic fold as it is generally noted otherwise. The voidspren Ulim was also described as having Shin eyes. It is also the way Odium himself is described.
Why did the dawnsingers switch to following Odium?
What exactly did the humans do to the dawnsingers to make them seek Odium? In certain accounts (the Eila Stele, possibly a few death rattles) it seems like the humans are seeking to destroy the dawnsingers. However, in other accounts (specifically the Eila Stele and the Listener songs) it seems like the humans sided with Honor and Cultivation. The best I can understand is there were either two groups of humans (one to destroy, the other to side with H&C) or there was some kind of time gap between the first and second desolation (the first desolation being the arrival of humans and the second being the revenge of the Fused).
But this kind of begs the question: what's going on with the shards?? It seems like there's NO WAY that Honor and Cultivation would be okay with Odium dropping by for tea and to destroy the world. So what were they doing during the clash between humans and dawnsingers? I can't imagine that HONOR and CULTIVATION would sit back and watch their people destroying each other?
It also seems like Odium did something to their forms. I don't know if he created the Unmade while on Roshar, but it sounds like they were involved in turning the dawnsingers. Take for example mediationform vs. envoyform. Mediationform made for peace, it's said. / Form of teaching and consolation. / When used by the gods, it became instead/ Form of lies and desolation. It's a leap, I know. But to me, it looks like Sja-anat currupted the spren that the dawnsingers would use to enter mediationform and therefore created envoyform.
Why did Honor/Cultivation switch to supporting humans?
So what is this big betrayal which the Listeners remember in their songs? The best I can tell is they're pissed that 1) H&C told them to take the humans in and 2) the Honor created the Honorblades for humans, instantiating the Oathpact. Now, I may be conflating the advent of the Heralds with the Oathpact but I think they're linked. If they are indeed linked, that means that there are already fused flying around which means that the dawnsingers have already switched sides and are on team Odium.
There is an other possibility: that H&C were aware of all three inner-planets in the system. What if H&C were ALREADY gods to the humans who escaped the destruction of their world? What if they were merely consolidating their forces against Odium as he came to call.
What about the Surges are so dangerous?
This is part where I'm going to go a little meta. Brandon is always extremely specific in his wording for texts like the Eila Stele (please see Alendi's Logbook and Kwaan's inscription for examples). Here is the text which concerns us: They came from another world, using powers that we have been forbidden to touch. Dangerous powers, of spren and Surges. They destroyed their lands and have come to us begging. So this text is being written by someone looking in on a magic which they may not know from the outside. They are inferring that it's like surges, but I think that can't be the case. The surges in Roshar are unique to the planet, as far as we know. As far as we know, the dangerous power is worldhopping itself. The reader can imply that it was surges which destroyed the human's original world but the text doesn't specifically say that.
The greater contextual significance of Roshar
In the second letter, the author says, "The worlds you now tread bear the touch and design of Adonalsium." I'm taking this to mean the Rosharan system, not the entire cosmere. We know that there are other Shardworlds created specifically by the shards who inhabit it. Therefore, I think if it were the case that the author wanted to allude to the entire cosmere, the letter would have read, "The worlds you now tread bear the touch and design of the power of Adonalsium." I know I'm splitting hairs and possibly being pedantic, but bear with me.
What is the significance of Roshar being specifically designed by Adonalsium? Right off the bat, this would be the first world we've seen where shards shaped his existing investiture rather than creating their own. In her essay on the Rosharan system, Khriss theorizes that there are certain aspects of the world which existed pre-shattering. The storms would be one of those phenomena. She does note however that the interference of H&C makes it hard to tell what was around before they showed up.
It seems like there's something significant about Roshar. We know Odium has a plan. He had a hit list and he seems to be following it. That means he's going after shards, but it also looks like he want's to destroy the world itself. I don't know if this is because he's become to invested in the system or not.
tl;dr: I think we're only getting one side of the story
