Board Thread:Warhammer 40k General Discussion/@comment-25618639-20150807010020/@comment-50.67.10.44-20160324063101

It's possible that it was a combination of stories.

I suspect that the Emperor was already a highly gifted and powerful psyker in his own right before he entered the warp gate at Molech. We do know that the Emperor is VERY confident (some would say downright arrogant) about his abilities and his vision for humanity. It's possible that he stole/acquired/found something in the Warp that he needed to create the Primarchs, something which boosted him to a god-like level.