"Once, the Sith Empire ruled over 120 habitable worlds across an expansive area of the outer rim. Founded by a relatively small group of exiled Dark Jedi, who arrived in Sith space without weapons and in a single starship, this Empire was a testament to the greatness of the ancient Sith Lords." ―Kla
One thing people may be unaware of is that there is a sith species and a sith religion. Whilst they are separate and the sith species came first, the sith religion was founded on the home world of the sith species.
The Sygian Caldera that surrounded the region made it a strategically strong position. It was extremely hard to navigate and would assist in the protection of any empire controlling the region. Whilst this did help keep the region isolated from the rest of the Galaxy, it was actually much harder to navigate out of the Sith World, then it was to get inside the sith worlds.
The Sith Worlds is the home place of the Sith Species home world, Korriban. In its earliest recorded history a Killik colony was established on the world. This colony produced, and was led by, a Killik Sith Lord. The sith species, however, managed to quickly drive the colonists off world reclaiming the planet as their own.
Whilst the Killiks were the first to try and claim Korriban, and the sith worlds in general, they would not be the last. The next contender was the Rakata Empire, which invaded the planet in an attempt to integrate it into the greater empire. The Rakata’s would, however, equal fail in their attempts when the Sith King Adas lead his people to drive off the Rakatan. Though the Sith successfully drove off one of the largest empires to exist at that time in the galaxy, they lost their king in the process. The ensuing centuries of Sith society fell into strife. In this time the sith of Korriban, with the use of captured Rakatan ships, began relocating to other planets in the region and even beyond.
The strife in the Sith Society allowed Xim’s Empire to come to rule over the region until the demise of the empire at the hands of the Hutt Empire. Once more the Sith Worlds would fall into obscurity for nearly 20,000 years. At the end of the Hundred-Year Darkness, fallen jedi, fleeing a battle, re-discovered Korriban and the Sith Worlds. The fallen jedi amazed the sith species with their force abilities, elevating the jedi to god status in sith society. Years of the Fallen Jedi inter breeding with the sith species meant that Sith not only meant the Sith Species, but also the fallen jedi.
These “Sith” created the first Sith Empire within the sith worlds region, the lack of knowledge of the region to the greater galaxy was there natural protection. After a number of unremarkable leaders, the sith empire came under the Control of Darth Naga Sadow, who used sith magic to assert his position and turn Korriban into a hellish landscape. This event was accompanied by the arrival of two Hyperspace trail blazers, the Daragons. Using this new route, the Sith Empire began the Great Hyperspace War, coming out of the shadows and, for the first time, revealing the Sith.
The sith Empire would ultimately fail in this war however, with Naga Sadow going into self exile on Yavin 4. Another repercussion of the war was the near extinction of the Sith Species, who now existed on small enclaves throughout the galaxy. The Sith Worlds would come to be the religious and political centre of nearly every sith empire to follow the 1st sith empire.