Ultramar Subsector

The Ultramar Sub-sector is the charted administrative region in Ultima Segmentum that contains Guilliman’s Five Hundred Worlds of Ultramar. It forms a realm within the Imperium, and its inner systems include Macragge, Konor, Iax, and Espandor. Unlike most Chapter fiefs, it comprises an entire settled region with its own auxilia (auxiliary military forces), defence fleet, and Tetrarchs.

The Great Crusade extended the realm to its present scale. The Shadow Crusade and the Ruinstorm later brought it close to isolation from the rest of the Imperium, and Imperium Secundus, an emergency state, was established within it. Behemoth, Honsou, the Black Legion, and Mortarion’s Plague Wars have each since attacked the sub-sector. Guilliman’s return reopened the question of the old borders and led to Shield Chapters being stationed across the region, which remains more self-sufficient in food than most of the Imperium.

The sub-sector holds standing as the one Imperial region that operates as a working state. Unofficial fan maps retain Ultima Segmentum as its parent region and list Calth, Talassar, and other systems as children of the sub-sector, rather than reducing Ultramar to Macragge alone.