Necromunda is a Hive World in the Segmentum Solar and a major producer of munitions for the Astra Militarum. The workshops of Necromunda continuously produce lasguns, autoguns, shotguns, and boltguns for the famous Adeptus Astartes. The planet also provides large numbers of soldiers for the Astra Militarum, such as the "Necromundan Spiders," as well as other supplies.

Necromunda is typical of most hive worlds; resources are scarce, life has little value, and its cities teem with powerful gangs. Welcome to the Underhive! The workshops on Necromunda are located deep beneath the planet's surface, and these lower areas are referred to as the Underhive. Filled with a network of intersecting corridors and passages, the Underhive forms a labyrinth of pathways and steep drops into endless caverns.

A dangerous place to live, the Underhive is rife with crime and violence, and is controlled by many Clan Houses or "Gangs." The odds of survival increase significantly by joining one of the many gangs that dwell there.