These meditation chambers were the personal chambers of Darth Thanaton. The chambers consisted of many rooms, however, its greatest detail was the large room in the middle, with a platform and many large Sith statues around it.
The meditation chambers of Darth Thanaton were only accessible to Thanaton's followers and students. There, the various apprentices and Thanaton himself meditated over the dark side of the Force. During the Cold War, Kallig confronted Thanaton after the latter tried to kill him. Kallig killed Rolan, one of Thanaton's apprentices in a duel. After Thanaton was killed on Korriban, Kallig took over the Chambers.