Oh waitasec - Molech IS where Knight House Adam Devine was established, the obvious but shhhhhh eventual followers of Slaanesh. They appeared in a short story as well, something to do with one of the sons of House Device becoming an incubator for a demon while sequestered in the hold of a space ship.......I dunno, can't remember much detail, but they were all SURPRISE Slaanesh worshipers, and there was a young orphaned girl involved with a pre-Grey Knight Errant of Malcador.......
There's a lore story for Big E, might even be the short story 'The Last Church' or in Horus Rising, as indeed, the Big E is a divine construct made of the life force of all of earth's shamans, from, like, waaaaaaaaaaaay back when (allegedly, before recorded history, He has been around since Shamans were shamans, but bide His time until he could reveal Himself).
I am gonna have to read Vengeful Spirit again, cuz I don't remember any of this lol.
Side thought: wasn't a female inquisitor turned in to the Red Angel in the Ultramarines Omnibus, through Daemonica Speculum (can't remember the name for $#!t). in your post, are you referencing Angron as the Red Angel? Crapo, I really need to reread the book. I believe the Red Angel is also used to describe Sanguinius, as well as one particular demon, and Angron, and the converted female character I mentioned: she goes on to destroy a whole OTHER FRIKKIN UNKNOWN GALAXY BY HERSELF/ITSELF and then reappears after this heretofore unknown carnage like 'hey, whatsup?'
I believe ALL primarchs have some level of psychic powers, be it from an aura of control to outright psychic shenanigans..... that they could even sense each other psychically...
Yeah, ur post is great, mine sounds like a 3rd grade book report...