Susa is Assyria III, a silicate terrestrial planet with some 1.4 billion inhabitants.
Physical Geography
It has a thick atmosphere and rugged, very mountainous terrain. Oceans cover about 26% of the surface. Its atmosphere has ample oxygen, but it is not breathable at sea level due to the high partial pressures of oxygen and carbon dioxide. Atmospheric pressure at sea level is about 3 atmospheres, colonization is focused in the upland regions where the atmosphere is breathable with carbon dioxide scrubbing. Some species of introduced Earth vegetation grow abundantly on Susa and it covers much of the planet where temperature conditions are suitable, making it one of the few planets in the Allied Worlds to have an extensive 'feral' ecosystem. Temperatures on the planet are uncomfortably but not intolerably high. It often reaches the 50s C in the summer months at equatorial latitudes. The atmosphere is humid with frequent rain in most regions, often somewhat acidic due to the presence of sulfur oxides in the atmosphere. Feral rats have adapted to the planetary environment and are very abundant in the jungles of Susa; the plant species surviving the dark age are all ones that can manage to survive despite the tremendous abundance of rats.
Susa is tectonically active, with numerous volcanoes and frequent earthquakes in many areas.
History and Culture
Susa was a successful colony in the Imperial era, and the first world colonized in the region, but a catastrophic war with bioweapons in the early Dark Age decimated the human population. The survivors regressed to a primitive level of technology whose survival depended making chemical carbon dioxide absorbers and gathering from the introduced terrestrial plants. Susa was essentially colonized by Larsa after advanced spaceflight reappeared there, and the Susan population is divided ethnically into 'Survivors' and 'Larsans.' Centuries of interbreeding have reduced actual racial differences between the groups and in any case social relations are not very strained in modern times. Susa was granted self-government early in the history of the Allied Worlds.
Today, Susa enjoys a rapidly growing population due to both birth and continued immigration, from Larsa and beyond. The planetary government has historically restricted immigration, fearful of Susan institutions and infrastructure being overwhelmed, but the policy has substantially weakened lately, and many people are attracted by the abundant vegetation, almost-shirtsleeves environment, and relatively low population density.
The Susan wormhole gate, in orbit around the planet and connecting it to Guller VII, was destroyed by a rogue worldship, cutting off the Twelve Worlds from connected space. Some debris from the destroyed gate remain in orbit to this day.
Economy
Susa is self-sufficient in most respects, importing only a few high-technology and luxury items. Premium agricultural goods, e.g. dried fruit, are sometimes exported to Larsa and Shamash where they enjoy a great cachet with the upper classes. Susa is one of the few worlds to enjoy noticeable income from interstellar tourism, though the high cost of such transportation makes it a once-in-a-lifetime experience for even most of the upper classes. Visitors originating from Larsa are more common; most of the interstellar visitors are from Mars or Heidelberg.