The first thing I would like the point out is that, this is something that came to my mind this morning when I was unable to sleep due to the heat in the UK at the moment, it could be very flawed and I could have had many things really muddled up. But, with everyones input and thoughts, I am sure more sense could be made out of this.
Outside of the books, I must admit I am unsure with how much has been revealed from Sanderson himself, most of this could be unproven or thrown under the rug, but I think it's intersting.
So, I have a theory about the Unmade, The Heralds and Honorblades.
Basically, the history of the Unmade is very cloudy and in modern Roshar, their history is largely unknown. Some sources claimed there was 10 but it is generally assumed that there are 9. This I think is very interesting and quite important. There are 10 heralds, and only 9 Unmade (but there could be 10, see what I am getting at?).
Ever since the Oathpact was abandoned, only 1 herald went to Braize, being Taln. This means there are 9 Heralds left on Roshar, incidentally there are 9 Unmade. I think there is a link there… I do believe that there are 10 Unmade, and even though sources indicate that they have existed on Roshar since before the Desolations, I debate how true this is (backed up by the clouded history).
I think, in previous Desolations when the Heralds were trapped on Braize, they were being tormented and fighting against a specific Unmade (one per Herald, and its Voidspren). After the Oathpact was broken, and only Taln went to Braize, his Unmade went with him. Thus, 9 Unmade were on Roshar with the 9 Heralds, and 1 on Braize with Taln.
[Off topic I thought of in my edit, but, the Unmade could be Odiums ‘Heralds’. We have seen the Fused use surges, maybe there are different types of Voidspren, similar to the different Spren needed for each order of Radiants: Honorspren, Cryptics, etc.]
For whatever reason, the Voidspren remain trapped on Braize as long as one Herald and Unmade are present. (This I can’t seem to find a logical reason for, but I think it is important, something about a Herald being on Braize keeps them trapped, even if it is one Herald.)
After Taln had given in, and returned to Roshar, everything on Braize was freed. Thus, the coming of the True Desolation. This also means I think a 10th Unmade has come to Roshar, one that has been ignored. (this backing up some sources from history that claim there were 10).
This was the first thing I have been thinking on. Secondly, Moash and Honorblades.
Moash killed Jezrien in a way that is unlike that in history, when a Herald got killed in history, they seemed to return to Braize, however, Moash killed Jezrian with a knife that contained a gemstone. I think Odium has been cunning in his planning. 4500 years had passed since the last Desolation, the longest time in history; this is A LOT of planning time.
We don’t know much about the creation of Honorblades, and we know Shardblades are Spren that mimicked Radiant surges, but Honorblades are said to be a type of Splinter of Honor. I think however, Odium has found ways to create an Honorblade out of the Herald itself. This would be interesting, if the gemstone in the dagger Moash used has bound the herald, (also confirming this death being ‘different’), then perhaps that gemstone can be used to create a new Honorblade.
And this could have interesting implications, imagine if his new Honorblade/Heraldblade?, allowed the wielder to become to new head of that order of Radiant. Imagine if, it actually allowed them to manipulate and ‘control’ the knights under that order; it would really mess up Dalinar’s plans. I feel like Moash will also be the first person to wield this. I find it too strange the Jezrien (being the order of windrunners, thus Kaladin, Moash’s ‘friend’) is the first Herald to be killed in this way.
If a new kind of power is created from Jezrien, and Moash wields it, then, he could take control of the Windrunners, and if he is able to somehow influence them, he could turn them against Dalinar. And Moash being Moash, will probably try to convince Kaladin that this is the ‘right’ thing to do.
Ironically, this could be what leads to Kaladin debating breaking his oaths, as what Syl and the Stormfather have been promising would happen, but this time, in a way that is ‘different’ to The Day of Recreance.
Since this is the True Desolation, it would make more sense that things would turn out differently to how they have in the past, ESPECIALLY with this additional time Odium has had to plan.