The Umbral Sea is a region of space in the gulf between the Peripherian League in the east, and the Empyrean See in the west. Largely considered to be a lawless borderlands, the Umbral Sea is home to numerous independent polity's and organizations; it's trade routes plied by plucky free traders.

Human habitation in the Umbral Sea can date back from humanity's earliest deep space colonial efforts, seeding the region with fledgling, hopefully colonies. However after almost four hundred years locked between two competing political powers, the Umbral Sea has become a hive of piracy and proxy wars.