Board Thread:Warhammer 40k General Discussion/@comment-4851119-20140118095944/@comment-24944355-20141016051240

I have always had a sneaking suspicion that the surviving missing primarch is the secret power behind the Tau. As for both legions being completely destroyed, unlikely. Every legion during the heresy has members who chose the other side so whatever happened to their primarchs the marines who chose the Emperor would still have to be dealt with and I can easily see the survivors being rolled into the Ultamarines. They are after all not only staunchly loyal but the most generalist of the legions & would be able to absorb legionaries from other legions more easily than any other.