Isolation chambers

The isolation chambers were hidden rooms housed in the subterranean galleries beneath the temples on Yavin 4 built by Naga Sadow. Their purpose was to host the Massassi warrior Kalgrath, who was put in hibernation in 3996 BBY. The chambers contained a suspended animation capsule and a primitive computer in which part of the history of the Massassi was preserved. A secret underground corridor to the rooms was located behind a blank wall in the Great Temple main hall, which had become the Massassi Station's hangar by the time of the Galactic Civil War.

Shortly after the Battle of Yavin, a TIE/sa bomber starfighter of the Galactic Empire crashed in the Massassi ruins, which caused damage in the isolation rooms and woke up Kalgrath. The hero of the Rebel Alliance Luke Skywalker used the Force to open the blank wall and discovered the isolation rooms, where he learned about the ancient Massassi and their last guardian.

Text and facts from the “Isolation chambers” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.