Board Thread:Warhammer 40k General Discussion/@comment-67.197.44.118-20130216115719/@comment-3580035-20130411054002

I forgot the source of this, but I do remember a case where Space marines and Chaos marines allied together to destroy attacking Tyranids. Whilst they had been fighting against each other before the Tyranids arrived, and again after the nids were destroyed, it is a rare example of an Imperium and Chaos alliance.