Catachan System

The Catachan System is the death-world star system in Ultima Segmentum whose jungle planet is the yardstick other death worlds get compared to. Catachan eats colonists, tanks, and, on a bad day, Space Marines; Jungle Fighter regiments are the planet's only export that leaves alive.

There is little else in the charted well: one green hell and the void around it. The Imperium does not civilise this system; it harvests survivors. Catachan-born Guard turn up in warzones that make other worlds look tame, which is the whole point of keeping a pin on a place that wants everyone dead.

The Catachan System still matters because the Guard will never stop needing people who treat a Tyranid biome as home. Unofficial fan maps keep the Ultima parent and do not invent extra colony worlds to make the system look busy.