The Calixis Sector is home to a single Chapter of the Adeptus Astartes, the Green Knights Chapter, which is based on the world of Phagir in the Hazeroth Sub-sector. Based upon Imperial Fist gene-stock the Knights pay only lip service to the Codex Astartes. Created in M38 as part of the 23^rd Founding the Green Knights had already established themselves as strong and fearless fighters by the time they were assigned to Lord Militant Angevin's Crusade. As compensation for their part in the conquest of Calixis they were granted rights to a homeworld.

Unfortunately for the Green Knights their home-world was ravaged by a terrible genetic virus several decades ago. This has left their world without any higher life-forms, including human inhabitants. The end result is that unless the Knights can find another home they are doomed to extinction. In the meantime the Chapter has taken to recruiting while in the field; rounding up potential candidate in whatever war-zone they are in and 'offering' them the opportunity to become Marines. This is a not entirely legal procedure, but desperate times leads to desperate measures.

Their main fighting strength (such as remains) is currently deployed somewhere near the Eye of Terror in preparation for what looks like it might become yet another Black Crusade.