I have a question if you don't mind me asking.
If you were to do a 40k story where you made a primarch character based on Kokushibo (Michikatsu Tsugikuni) from Demon Slayer, would you do them as either loyalist or traitor or do you see them being on neither side?
I was just curious about how a kokushibo primarch would play out. I was thinking what if he was a early attempt at making the primarchs/matriarchs, but was the first surviving result. As a result of this, he wasn't as powerful as the primarchs and the emperor/empress considered him either as flawed or as a failed experiment.
Due to this he is either ignored or mistreated by both the primarchs/matriarchs and the emperor/empress. This treatment would result in kokushibo seeking to get stronger to prove them wrong.
That's all I have got for the idea so far. I don't know if they would look to the chaos gods, necrons or even the tyranids somehow for power