So having just finished Darkness in the Blood I have a lot of questions that basically boil down to 'is this for real / trustworthy?'
We are given a definitive answer as to where Mephiston's powers come from, and his new/current status after the Primaris transformation.
We get a clear, logical explanation for what the Sanguinor is (and his darker shadow).
We even get a clear answer to 'is Sanguinius still alive somehow' although that part is pretty weird.
Also the most interesting part, that goes by very quickly but might be the most important, is a brief line or two stating that Abaddon may not end up being happy about what he has unleashed with the Rift and general warp crap. I read that as talking about how the Warp gods have their own plans but also as an allusion that the "good" warp stuff can now exact more influence as well (Ecclesiarchy miracles, the Sanguinor, etc) It reminded me that in one of the other recent books one of the Adeptus Custodes with Guilliman, during a massive display of power by an alleged saint, pauses and addresses it as "My Lord..?" with complete shock. I may be quoting that wrong but he very clearly thinks for a moment he sees the Emperor at work, and Custodes are not easily tricked or surprised.
Anyways, back to this book - It just... it's a lot. And I think there are legitimate questions about whether there is trickery/misguidedness involved. I was not expecting so many big revelations about Blood Angels mysteries all in one book.
Not to mention, IF the info on the Sanguinor is legit, then why wouldn't all Chapters that are old enough have some kind of Warp mascot?