The Falls of Marakross (Tales from the Dark Millenium) (Warhammer 40,000)

An uprising of heretic cultists on the world of Cordassa brings the Dark Angels Chapter of Space Marines to the world. But is their mission to help the beleaguered defenders of the troubled planet, or do they have their own agenda? Only Interrogator-Chaplain Artemius knows, though Inquisitor Mattius Heiron has his suspicions, and will go to any lengths to learn the truth.