These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Iron Woobie: Astorath the Grim is in charge of killing the fallen Sons of Sanguinius, and will do his duty, even though it's made clear he loathes it.
Tear Jerker: The Horus Heresy novels focusing on the Blood Angels reveal some horrifying facts. The Red Thirst isn't a "new" phenomena, but actually emerged during the Great Crusade. Sanguinus desperately hid this condition from the Emperor because he strongly believed this would result in the entire Blood Angels Legion being obliterated. And the Fan Wank that Sanguinus could restore the Legion back to sanity? Proven false in a heartbreaking scene where Sanguinus personally tries to bring a Blood Angel who has succumbed to the Thirst back... and fails, utterly.