Board Thread:Warhammer 40k General Discussion/@comment-24383134-20140221011621/@comment-4264245-20140221125944

1) Lorgar was a psyker, although he didn't master his powers til Istvaan V Dropsite Massacre. He invented Imperial Tarot, btw.

2) Kor Phaeron used to be a high-tier priest of that Old Faith of Colchis, and secretly worshipped Chaos. When the Emperor rebuked Lorgar, he and Erebus convinced their Primarch to "look for true gods" and so the Serrated Sun Chapter went into the Eye of Terror, coming back turned into Possessed Marines. Soon after, Lorgar went there too and was chosen as the prophet of the Chaos Gods. So yes, Aaron Dembski-Bowden's The First Heretic talks about Lorgar's corruption. Nuff said xD

3) Lorgar wouldn't have commanded enough respect from his fellow Primarchs to lead the rebellion on his own, so he had to choose a suitable visible head - Horus.