Canon Warhammer Bits that Make Me Crazy Pt.1
Perturabo canonically cannot stand anything that he builds because it never lives up to the vision that he has in his head. His room is filled with miniature models of buildings and other knick knacks he's designed. Hates the other primarchs because he cares about his boys getting recognition, not just himself. He kind of sometimes genuinely seems to care about the Iron Warriors. Other times he literally decimates them as punishment so ya know.
Fulgrim canonically staged his own attempted assassination at the hands of a raven guard sniper in order to convince Perturabo to join him in the Eye of Terror (for chaos reasons). But the way that he did this was to have Perturabo build a full auditorium and stage for him to monologue on first. Classic. (He also canonically had a pear of anguish shoved up his ass while his sons tried to exorcise a demon from him - just...just google it man idk).
Konrad has an eater of dreams that stays with him and brings him back from his visions. He also keeps corpses strung up in his room and talks to them and notices whenever anyone moves them (and gets very upset about it). He also ate dogs growing up, but that's not surprising. The closest he came to dying (before actually dying) was when Lion broke his spine and carved him open - during Konrad's surgery Sev notes that the medicae are discussing organs he's never heard of, suggesting that Primarchs have all kinds of wacky stuff inside them.
Dorn is one of the only Primarchs who leave astartes and other teams behind on conquered planets in order to help set them up as part of the Empire with long-term success. This is also partly why the Imperial Fists recruit from many different worlds, which is fairly rare among Primarchs. (I've posted about this before but) He also constantly makes himself smaller and quieter when around humans to be considerate of how he affects them.
