Disclaimer: I'll be citing many things I read in the course of time, but I lack the energy to reference WoBs or other theories, so I apologize if I talk about something that has been confirmed as incorrect!
Hey! First post here After finishing Rhythm of War and spoiling myself a lot through many reads of coppermind, I spent this whole year reading through cosmere theories over here and on reddit too. I'm a huge fan of many theories that are around, and one of the things that I'm really curious about is the origin of the unmade.
There are many theories around, some a bit more elaborated than others. There is one linking them to the dawncities (mostly based on what the Sibling said about Raboniel unmaking them) and though I like it, I think it'd be a bit of a stretch (perhaps I'm wrong). There are also many theories linking them to the Heralds but for some reason I don't feel super happy about them either...
However, yesterday I was reading a theory on Ba-Ado-Mishram having a human/singer part called Mishram (because of stuff like how she was called a "highprincess" or how Kalak talks about Mishram in such a coloquial way) and that got me thinking. Maybe this is a bit of a stretch, but we could say that Heralds more or less are spren, in the sense that they are cognitive shadows and we know they get affected by Roshar's population's conceptions about them (I think this was confirmed on a WoB but I might be wrong). I always assumed the Unmade were originally a spren of high tier like Cusicesh or even higher like the Stormfather or the Nightwatcher, but what if they were actually people, or aspects of people?
When talking about lesser spren, we know of the nature ones just like flamespren, windspren, etc. and the "emotion" ones like angerspren, joyspren, etc. In this tier we also have creationspren, logicspren and some others that don't really represent emotions but something more like concepts. Then we have the "truespren" or what we could call the radiantspren. I'm not really sure what are they, I think it was confirmed on a WoB that the 9 kinds were created by Honor and Cultivation (though I know spren in general predate the arrival of Honor and Cultivation to Roshar). So, radiantspren might be the cognitive representation of ideals ? I mean, for honorspren that's quite straightforward of the ideal of honor (not as a shard but as a general ideal) but mistspren, cryptics, inkspren, etc. are more hard to tie to a specific ideal, though we could say ALL radiant spren are tied to the ideals represented by the radiant order associated with them.
Relating the last thing to the Heralds, we know there are certain ideals of values tied to each one (creativity and honesty for Shalash for example, I don't recall the other ones). Maybe this ideals used to have a spren of some sort, or maybe the cognitive nature of the Heralds got tied to these values because of how long people associated them. There are many theories around that link the Heralds' madness to their ideals, and there's a WoB confirming their madness is a magical one. What if the unmade are an aspect of the heralds that was taken from them by Odium, causing their madness and also explaining how many of them are mindless and represent specific "bad" things like Ashtermarn or Nergaoul?
There are a couple of problems with this theory. First, we should establish when this happened. I don't know how old the Unmade are, so I'm asking you guys, does this make sense chronologically? In Dalinar's vision fighting the Midnight Essence, the KR already existed but we know the Oathpact and the Heralds predate the KR. My theory would be that Odium unmade the Unmade when the Heralds broke the Oathpact (explaining why there are 9, since Taln didn't break), but I'm not sure when this happened. It could have happened after Honor's death maybe?
There's also another problem: as far as we know, the 10 Heralds are insane. If the unmade were part of the 9 that stayed, Taln shouldn't be insane, but he is. We could say he is insane because he was tortured alone for 4500 years with no rest, but he regained clarity along with Ash in Thaylen City's battle, so probably his madness is magical too.
Anyway, sorry for the wall of text and let me hear what you think!