Board Thread:Warhammer 40k General Discussion/@comment-67.197.44.118-20130216115719/@comment-3258762-20130216173651

But, Supah, the large majority of the Alpha Legion is not in the warp, but are roaming the galaxy, raiding and pillaging (and infiltrating) Imperial planets and worlds.

But I agree nontheless, I doubt any cell other than the one which has Omegon (If Omegon is not in the warp) has turned to the warp. Primarchs do seem to have a surprising ability to keep people from Chaos :3