It is in a rotationally locked orbit around its sun, meaning that one side of the planet is a sun-baked desert, while the other half is locked in a perpetual night, an arctic hemisphere. Despite its unusual orbit, it is one of the system's main life-supporting planets. The majority of the population lives within the "Shadow Belt," the equatorial region that lies between the two extreme hemispheres. There are inhabitants on both hemispheres, although they lead somewhat harsh lives. There are two main cities in the Shadow Belt, one based over one of the inland oceans fed by the dark side's glacial movements, and the other, Skitterfall, which is recognised as the planetary capital due to the fact that it contains the largest spaceport[1a][1b].
The Adumbrians have over thirty different words to describe twilight conditions (including "Skitterfall"), each describing a degree of difference that is virtually undetectable by those not native to the planet[1c].
- 1: The Traitor's Hand (Novel) — Ciaphas Cain: Hero of the Imperium (Omnibus) by Sandy Mitchell