The Imperial Citadel became the new base of operations for the Sith survivors after the conclusion of the Great Hyperspace War. The individual who would later be known as the Sith Emperor spearheaded their relocation to this location.
Within the initial century following the Sith's withdrawal to Dromund Kaas, they undertook the construction of Kaas City, situated deep within the jungle. This city served as a symbol of the restored Imperial society that had been lost during the Great Hyperspace War. At the heart of this city stood a formidable citadel, known as the residence of the Emperor and the Dark Council.
As the central hub for the Imperial government, the citadel housed the main offices for the Ministries of War, Intelligence, and Logistics. Furthermore, the citadel accommodated a type of Mandalorian diplomatic mission, referred to as the Mandalorian enclave.
Around 3678 BBY, a representation of the Great Hyperspace War Bas-Relief, or a similar artistic depiction, was prominently displayed on a wall within the chambers of the Sith Emperor.
The Imperial Citadel situated on Dromund Kaas existed in two distinct iterations. The initial citadel's construction commenced soon after the arrival of the Exile fleet on the planet in 4980 BBY. The original design bore resemblances to both the Sith Academy located on Korriban and the Sith Citadel on Ziost. However, before construction could proceed, the land designated for the Citadel and Kaas City required clearing of dense jungle and the dangerous creatures inhabiting Dromund Kaas. Odile Vaiken, who would become the father of the Imperial Navy and the first Grand Moff of the Empire, reportedly killed a ferocious terentatek on the very ground where the Citadel was eventually built. It functioned as the Empire's seat of power until its destruction in 4043 BBY during the Kaggath between Darth Qalar and Darth Victun. The Dark Council executed both Sith Lords, and Darth Nostrem was tasked with overseeing the citadel's rebuilding.
The Sith Emperor personally designed the second citadel, which differed substantially from its predecessor. It no longer imitated the earlier citadel designs. After its completion, Darth Nostrem was confined within its depths to assess the new citadel's intricate defenses. The Sith Lord was unable to escape and ultimately perished.