Board Thread:Warhammer 40k General Discussion/@comment-6078851-20130318203252/@comment-6134883-20130326203834

I'm not so sure. It is indicated that the Rout has fought fellow marines before Prospero but not the result. As far as I can tell though there is no set canon on the 'Lost' Primarchs on purpose and never will be so we can let our imaginations roam.