I personally consider it discarded, but I got downvoted earlier for stating it as fact. Some degenerates cling on to it as canon cause it's on the wiki, even though it's basically discarded nonsense.

I mean why would they ever reveal the emperors TRUE origins? And to mention the story is super lame. A bunch of shamans are getting eaten by demons so they drink a bunch of poison and flood the warp with their souls? That would be a fucking feeding frenzy for demons. But apparently they were so bright that Chaos demons, and their Chaos gods, just decided to back down. Why didnt the eldar just do this? Oh wait its cause Slaanesh was able to consume most of their races souls in the blink of a fuckinf eye. Why doesnt every race with psykers do this? Why not do it multiple times? That's why they leave it vague cause it creates a billion plot questions/holes.

And it only takes a couple thousand human souls to create the goddamn Emperor of Mankind??? A being powerful enough to defeat C'tan? He punched the fucking void dragon across the solar system into the core of Mars, and imprisoned him down there! How the fuck can anyone consider this guy human?! The being that consumes 10 000 souls a day just to keep his fucking skeleton in a state of limbo between life and death?