The Adepta Sororitas, colloquially called the "Sisterhood," whose military arm is also known as the Sisters of Battle and formerly as the Daughters of the Emperor, are an all-female division of the Imperium of Man's state church known as the Ecclesiarchy or, more formally, as the Adeptus Ministorum.

The Sisterhood's Orders Militant serve as the Ecclesiarchy's armed forces, mercilessly rooting out spiritual corruption and heresy within Humanity and every organisation of the Adeptus Terra.

The Tyranid hive fleets are a plague on galactic life. Pouring from beyon the fringe of known space, the xenos scour world after world, harvesting biomatter to feed their gargantuan hive ships. As more tendrils of the Tyranid menace uncoil across the stars, so Humanity encounters new bioforms they must battle. The Red Terror is such a beast.