Sullust is the main planet of the system and home world to the Sullustan race. The planet is mostly rock and caves as the cold temperatures make any planet growth on the planet impossible. The atmosphere of Sullust is extremely toxic as there are many volcanic regions which are very active causing a near constant out pouring of dangerous gases into the atmosphere. On average there is a volcanic eruption somewhere on Sullust at least once a week. The gases from the eruptions form noxious clouds that hover around the world giving the planet an extremely dark and gloomy look from space.
Because of the dangerous conditions on the planet's surface, the majority of Sullust's organisms live in caves. The Sullustans are extremely well adapted to their planet, building entire cities underground with thousands of kilometers of tunnels leading from each and every way. The Sullustans are highly advanced and their tunnel cities are considered some of the greatest architectural works in the galaxy. Hundreds of traders and galaxy roamers visit Sullust each month for the chance to walk around the confines of the caves. At least one company has employed Sullustan architects to help plan and build future underground colonies. The largest collection of underground caves and tunnels on Sullust forms the capital city of Suubria. Thousands of inhabitants live within the main cavern of the city.
The underground caverns of Sullust provide adequate amounts of plant and animal life to feed the Sullustan people. Most of the animals are small, fast creatures that feed off of the fungi growing in the caverns. Some of the caverns are also used as farming areas, allowing large amounts of fungi to grow for cultivation. The hunting ability used in the caverns of Sullust has led the Sullustan species to have a natural sense of direction.