The Imperium's farthest frontier sector, containing 437 star systems divided along a coreward to rimward line by the Imperial border. The region is dominated by two major powers: the Imperial Spinward Marches sector and the frontier provinces of the Zhodani Consulate. In the independent territory between the two powers lie two small states: the Sword Worlds Confederation, and the Darrian Confederation. Each follows its own diplomatic line designed to maintain independence from both the Zhodani and the Imperium.

The Spinward Marches has been settled since the 400s and is still a frontier sector. High-tech worlds are scattered among empty, fallow worlds; there is potential for exploration, exploitation, and development for centuries to come.