Ultima Segmentum

Ultima Segmentum is the largest of the five great galactic divisions, a colossal eastern expanse stretching from the Imperium's settled interior to the wild frontiers of the void beyond. So vast is it that a second Astronomican-relay fortress, the segmentum capital, is required simply to hold its many hundreds of thousands of worlds in loose communion.

It is a region of extremes and dire threats. Within its bounds churns the Maelstrom, that great southern warp storm, and along its distant borders lies the Eastern Fringe where the young empire of the Tau Empire expands and the vast bio-fleets of the Tyranids came drifting out of the intergalactic dark to devour all life. Whole sub-sectors have been consumed, their populations reduced to raw biomass.

Ultima Segmentum contains some of the most storied worlds of the Imperium, including the fortress-monastery homeworlds of many Space Marine Chapters. But its sheer scale makes it a land of isolation, where a distress call may take years to be answered and where humanity's grip grows ever more tenuous the farther one travels from the galactic core. It is a frontier without end, endlessly contested.