Board Thread:Warhammer 40k General Discussion/@comment-37.152.33.225-20131111163502/@comment-8881468-20131210112420

well to quote russ from the prospero novel

" Executioner" as his role, and that his legion was unleashed upon astartes before.

if we go through other heresy novels/stories we find that even other primarchs do not know the 2, others like malcador say that nobody talks of them anymore/that they have been ereased from imperial records (edict of obliteration)

that is quite harder with the heresy primarchs, as those were more known for their eploits in the imperium and their actions shaped the imperium on a greater scale.