The Xana Incursion was a desperate covert campaign conducted by a Legiones Astartes Blackshield irregular forces as well as a small force of Dark Angels against the recalcitrant Forge World of Xana II in 009.M31, during the galactic civil war known as the Horus Heresy. Intelligence had reached Terra that the renegade Forge World on the western fringe of the Imperium had reached an accord with the Traitor forces to supply the Warmaster's armies with vast output of arms and material. The bargain was to be sealed with the delivery by Xana of a number of newly created powerful Ordinatus class weapons undergoing final field tests. In what was effectively a suicide mission, a handpicked force of Legiones Astartes, including many Blackshields -- in this case Space Marines who have chosen to remai