The Imperial Citadel functioned as a clandestine fortress for the Galactic Empire. It was located on Byss, a planet situated in the Deep Core, and served as the covert throneworld for the Galactic Emperor, Sheev Palpatine. Mas Amedda, the Empire's Grand Vizier, withdrew to this citadel. There, he formulated the blueprint for the Imperial political doctrine of the New Order, intended to endure for a duration of 10,000 years.
Within the current Star Wars canon, the "Mas Amedda" card within the "Sith Information Guide" subset of the 2015 Topps Star Wars Chrome Perspectives: Jedi vs. Sith set, which Topps released in 2015, included a mention of the Imperial citadel. The Imperial Citadel was initially introduced within the Star Wars Legends continuity, debuting in the second issue of Star Wars: Dark Empire, a comic series. This series was penned by Tom Veitch, with illustrations by Cam Kennedy, and was published by Dark Horse Comics on February 18, 1992.