From reading these comments, I have a couple questions: Perhaps part of what Honor and Cultivation did was somehow force Odium to invest? Which raises the question - how does a shard invest or divest from a planet? We know investing can be accidental or purposeful, but divesting isn't really talked about. If one day, for instance, Harmony wanted to leave Scadrial to help in cosmere related events, short of turning the whole planet into a starship, how would he leave the planet to help?
Odium's goal has to be twofold:
1. Shatter Cultivation
2. Leave the planet.
If his shardpool is linked to Braize and he is, therefore, invested there, how can he sever that connection? As far as we know, no one living is in the physical realm there (correct me if I'm wrong). The souls of the singer ancestors are hanging out in the cognitive realm we've theorized, but why are they there? how did they get there from Roshar? If the Everstorm is Odium's perpendicularity, how was it summoned and, again, how does it connect to Braize?
As for shardpools and perpendicularities maybe or not being always the same, I agree with the original author. Wasn't what Jasnah did to make it back to the physical realm described as making a mini-perpendicularity? Don't remember where I heard that, but I think that is so.
Also, I think Heralds guarding Odium's shardpool is a valid thought - until we hear from Taln I doubt we'll understand fully what was going on with the Heralds on Braize - "tortured" is such a broad word and how is was done and why it was necessary is still very much up in the air.