Board Thread:Warhammer 40k General Discussion/@comment-69.143.134.163-20150419161351/@comment-132.3.57.80-20150526183716

I'd add an interesting bit of spec - based on how some of the commentary is phrased in the novels (in particular the back and forth in "The Lightning Tower" by Abbott) its possible that during the horus heresy the remaining elements of these legions are known to still exist (at least to primarchs and Malcador). Perhaps even one or more of the primarchs was captured before being destroyed (and knowing the imperiums desire for secrecy possibly even still imprisoned not dead at the time). The warning that they are "lost to us" and "not to even think it" may imply that it could be changed - and the legions brought to bear.

Maybe their corruption was not so extreme or they were merely traitors and not chaos tainted?