"I know where it is. The planet is called Thule. Thousands of years ago it was an ancient Sith stronghold. Ulic fought there during the war. That's where the Dark Reaper is buried."
Thule was a semi-arid planet known for its rich savannas, continually bombarded by lightning storms, but Thule was also a hidden Sith stronghold. The rocky outcroppings which broke the plains were charred black from being hit by lightning. This charred rock later served as a form of sustenance for unusual, bioluminescent moss that made the rocks glow with an eerie light.
Thule was on the northern frontier of Xim's empire.
After the Great Hyperspace War, several Sith survivors fled to the world, where they would remain for generations, waiting for their revenge on the Jedi and the Republic. They established a military dictatorship, ruled by an oligarchy of eight generals.
With the rise of Darth Revan's empire, Thule was absorbed into its borders.
Around 1,000 BBY, LordKaan's Brotherhood of Darkness encountered the Chiss in the Unknown Regions and brought a legion of them to colonize Thule. Their descendants would spread out to the wider galaxy, although their species was still unknown to many. [3]
In 22 BBY, CountDooku went to Thule to revive the Dark Reaper in an attempt to destroy the Galactic Republic during the Clone Wars. A planetary shield enveloped the planet Thule, projected by the small moon Sivvi orbiting it. An attack led by the Republic resulted in the Battle of Thule and the destruction of the Dark Reaper.