Septemvius

A star-system on the eastern edge of the Ultima Segmentum, to the galactic north of the Damocles Gulf, Damocles Marches, T'au Empire and other locations in the Eastern Fringe. The path of the Aeldari Craftworld of Iyanden passes close to the system. During the Horus Heresy, the inhabitants of Septemvius VI (the only habitable and inhabited planet) allied with the xenos against the forces of the Warmaster. To this day trade between Septemvius and various xenos is not unknown and Septemvian culture, philosophy and even religion is less xenophobic than the wider Imperium. Because of this proclivity, Astra Militarum regiments raised on Septemvius are assigned a high-proportion of Commissars.

Septemvian military forces took part in the Damocles Gulf Crusade, including the Septemvius VI 4th Regiment (sometimes known as the Septemvius 4th or Septemvian 4th) which became the gue'vesa and later independent realm of Antak'ya.