After the fall of the Sith Empire, the Sith soon fell back to worlds unknown to the Republic or worlds typically left under the radar, leaving only Ziost and Dathomir as the two most obvious choices. Quickly assigning the remaining Dark Councillors of the old Empire to new positions within the Sith Order, the Dark Lord of the Sith has chosen to not carry the grandiose title of Emperor, instead taking on the true mantle of the Dark Lord of the Sith. The Sith Order is made up of four main branches below the Dark Lord himself, notably the Sith Academy, the Research Facility, the Military and the Intelligence Bureau, though these positions are much more free than the previous Sphere structure of the old Empire.
The Sith Citadel is a superstructure that contains the main research facility of the Sith Order and the Dark Council Chambers, along with the throne room of the Dark Lord of the Sith. Built on the desolate world of Ziost, the ancient citadel was built by the ancient Sith after the death of King Adas and conquered by the Exiles, and with the recent work of Darth Atrox to rebuild Ziost to it's former glory, the citadel has become stable enough to support the Dark Lord of the Sith, his servants, as well as the experiments of the research facility and the scientists.
The Orbital Defense Command Center was a military base located on the Sith-controlled planet of Ziost during the Galactic War. At some point, following the world's capital city's construction, the command center was constructed, and went on to serve a number of purposes, including, but not limited to, local headquarters for the Bureau of Intelligence, planetary customs, and air traffic control of the system, along with the Imperial Military.