Board Thread:Warhammer 40k General Discussion/@comment-98.81.158.208-20140213190331/@comment-5.69.236.255-20170329144004

There's also some suggestions from some of the newer fluff that Empy wanted to become a god in the warp, and was just using the teeming multitudes of mankind to fuel his ascension. Just like the traitors have always said...

It is now canon that he went to Molech during the Age of Strife (sublight, as it's close to Sol), and bargained at least knowledge of how to make Primarchs from the Chaos Gods. They must have been impressed with his gene-wrought immortal form so I think the deal was this: they'd let him walk as a god in the warp like they were, as long as he'd let them walk as demigods in the Materium like he was. Only the flesh of a Primarch could hold the essence of something so powerful as a chaos god. He may have intended to betray and sacrifice his "sons" all along.

Some have noted that Molech is similar to Moloch, the Caananite god of child sacrifice...