Board Thread:Warhammer 40k General Discussion/@comment-173.238.152.115-20140122073927/@comment-37.116.98.203-20150409145320

I think that (it's just an idea) the two missing Primarchs were for some reason erased (even before the meeting between Corax and the Emperor) shortly after they were discovered. Perhaps they were already too corrupted by Chaos, or they didn't agree with the Emperor's plans, or something like that... That could be why the two Legions have not fought anymore as so, but were (maybe) "subdivided" into the other Legions...