A fan story set in the world of Warhammer 40k, the Gray Knights, an elite army of demon hunters, storm an icy planet in the hopes of capturing an outpost and securing a place in the galaxy for future recruits and reinforcements. However, in the middle of an incursion on the outpost's further barricades, the mysterious Alpha Legion, an army of Chaos Marines, attempt to throw the Gray night squad into disarray. The Knight's leader, Castellan Crowe, wields the Black Blade of Antwyr against foes on all sides of his Purifier Squad.