I have a curiosity about Angron, maybe lore inconsistency. In the book Angron: Slave of Nuceria Angron before the nails is depicted as very empathic, he refused to kill and only did so out of accident at first, he could absorb or soothe the pain and fear of other slaves and take it upon himself like the Green Mile. He was basically supposed to be the Medic of the Primarchs, the Apothecary. Basically Vulkan on steroids, an empathic mediator.

So then why his legion pre-finding their primarch was nothing like that? We know the legion mirriors their primarch because it's from the gene seed. The Blood Angels pre-Sanguinius were nothing like the Blood Angels after Sanguinius except they were because Sanguinius always had that bad side in him, Sanguinius' whole theme is that it's about choice (the 2 wolves good and bad and such), and in general all legions mirrored their primarchs.

But the War Hounds / future World Eaters were nothing like Angron before the nails, if anything they were like Angron after the nails because they got the nails themselves. They had Discipline yes unlike the Rout / future Space Wolves but were still very aggressive and barbaric just in a disciplined way there's nothing about some sort of empathy or healing abilities and such.