Before around 5000 BBY, a rogue Jedi rebelled against the Jedi Order, believing that following the way of the dark side of the Force was the key to unlocking their full potential. The Jedi was cast out during an event known as the Hundred-Year Darkness. As a result of this event, the Sith were born.
During a period in which the Sith dominated the galaxy, the Sith had control of Coruscant, the capital of the Republic. The Sith constructed an immense black shrine over a light side vergence on a mountain at the heart of the planet no later than close to five millennia before 14 BBY. The Jedi eventually laid siege to the shrine, burning it to its foundations and defeating the Sith.
The Jedi built their own shrine over the Sith shrine's foundations. Eventually, the Four Masters erected the Jedi Temple above the former site of the shrine to contain the dark energy emanating from the corrupted vergence and metaphorically bury the Sith legacy. Over the following centuries, the Jedi Temple slowly took form. The ruined foundations of the Sith shrine were steadily buried beneath layers of plasteel and ferrocrete as a massive, flat-topped ziggurat was built around them.
Although the Jedi emerged victorious during the conflict, they would continue to do battle with the Sith over the ensuing millennia. While the Jedi falsely believed that the shrine had been destroyed, part of it remained deep underground; its insidious power would contribute to the near destruction of the Jedi Order around 5,000 years later.
In Star Wars Legends, the first conflict between the Jedi and Sith following their initial split was known as the Great Hyperspace War. The war made its first appearance in Legends in Tales of the Jedi – Dark Lords of the Sith 1 which was released on October 1, 1994.
The sourcebook Nexus of Power directly references a canon Great Hyperspace War. However, as it does so in the context of the contents of the in-universe mythical Qel-Droma Epics and no mention is made of an attack on Coruscant, it is not clear if they are the same conflict in canon.
- Nexus of Power
- "Before the dark times…" — Star Wars - The Official Magazine 101