The Imperial Sanctum, situated within the Imperial Palace found on Coruscant, became the primary location for the Galactic Emperor to conduct their business. This transition occurred after Palpatine's demise on the Death Star during the battle above Endor in 4 ABY. Positioned as a throne room below the primary chamber located at the Palace's peak, the Sanctum functioned as the Emperor's personal living space throughout his time ruling.
During the reconstruction of the Imperial Palace around 18 BBY, the Imperial Sanctum was established as the private quarters and operational center for the Galactic Emperor Palpatine. It comprised multiple areas, including the Emperor's personal study and sleeping quarters, a throne room, and Darth Vader's chambers. These rooms were predominantly utilized by Palpatine, Vader, along with their staff and assistants. The Emperor and Vader would frequently receive visitors, such as Prince Xizor of Black Sun, to deliberate on matters of significance within these confines.
Following the deaths of both the Emperor and Vader during the battle above Endor in 4 ABY, the throne room within the Sanctum was formally put into a state of mourning. A dark covering was placed over the throne during this period of instability. When Sate Pestage proclaimed himself Emperor, he took up residence in the Sanctum and occupied the lower throne, hesitant to move to the higher throne room due to concerns about potential dissent from other Imperials. It was during this time that Emperor's Hand Mara Jade managed to escape her confinement in the Palace and infiltrate the Sanctum. There, she absconded with the black shroud from the throne room, utilizing it as camouflage during her escape from the Palace.
After Pestage's removal from power, the Tribunal held court in the chamber previously occupied by the Imperial Ruling Council. Subsequently, Director of Intelligence Ysanne Isard leveraged her authority as the head of security to eliminate all competitors and seize control of the entire administration, effectively becoming Empress. However, she avoided the formal symbols of power, and her existing office assumed the functions of the throne room as a command center and venue for high-level audiences.
In contrast to the more ornate upper throne room, the command chamber had a more basic design and was notably large and spacious. The throne extended outwards on a lengthy, sharp-edged platform within the expansive area. The only access point was located at the far end of the platform, guarded by a pair of Emperor's Royal Guards.
Other areas within the Sanctum included the Emperor's office, which was plainly furnished with just a desk, a holoprojector, and a few valuable artworks. Similarly, Darth Vader's office was sparsely decorated, containing only a series of datascreens that provided him with updates on events occurring across the galaxy.