The Citadel stands at the heart of Kaas City, a monument to the Sith Empire's strength and home to its most powerful Dark Lords. The Ministries of War, Intelligence and Logistics are all headquartered here, along with a Mandalorian enclave. The Emperor's Dark Council gathers to meet in the Citadel when not on the Sith holy world of Korriban.
The original Citadel mimicked the designs of Korriban's Sith Academy and the Great Citadel on Ziost, but it was destroyed four hundred years ago when two members of the Dark Council fought an ancient Sith duel, called the Kaggath, on its grounds. The duel was a draw, and both of the combatants were executed by the remaining Dark Council members, who oversaw the rebuilding of the Citadel in its current form.