Page 81 of inferno in the section known as "The Darkest War."
If this is to believed whole expeditionary fleets, dozens of titan legions, and entire legion of astartes perished in the xenocide. The enemy only broken by the Emperor unleashing shit that laid in the "labyrinth of night." The Space Wolves, Dark Angels, and the Death Guard were fucking mauled I guessed in this action.
This sounds like fucking space nam'.