Board Thread:Warhammer 40k General Discussion/@comment-4851119-20140118095944/@comment-108.85.53.201-20140211050659

The lore states that Russ was sent to dispose of at least one of the Lost Primarchs. Their statues were covered up in the Imperial Palace and even the other Primarchs made an agreement to not talk about it. So if even Horus and Fulgrim wouldn't want to talk about it and they had already turned to Chaos, it must have been something really crazy like maybe one of them got seriously mutated or was courting with xenos. Even the CSM's hate the xenos. We don't know what happened to the other one and that is what I think is interesting. It lends to many suppositions and theories which is cool but I doubt GW will ever give us any details.