Board Thread:Warhammer 40k General Discussion/@comment-69.143.134.163-20150419161351/@comment-24037808-20150422132917

Newcomer question: is right to suppose that (following the "half and half" rule) one of the two Primarch was corrupted and the other loyal?

If so, it should be a lot more intriguing to investigate about the reason that took the loyal one to his fate.

A nice speculation could be that the two lost primarchs and their legions fought each other in the first grand brother vs brother war, and the loyal one was defeated after a feroucious and balanced battle.

That could explain why Russ got task to wipe out what remain of the corrupted victorious forces and why it seems it was not hard (could be that the Wolves fought not an entire legion, just what remain of it after the heavy losses inflicted by the previous battle).

If so, the 2 lost primarchs story could be the first glimpse that the emperor had about the "faulty" nature of his Astartes regarding Chaos tempation. So the Emperor had his warning about the future, and he simply underestimate it (as it happens in a lot of situation later on)