By the time of 3643 BBY, a group of explorers came across a long-forgotten Sith prison located within the underground passages of the world known as Dromund Fels.
Approximately in that year, someone involved in the ongoing conflict between the Republic and the revived Sith dispatched an associate to delve into the Dromund Fels catacombs and the prison. Deep within the prison, amidst a chamber overflowing with riches, the associate then found the perfectly preserved corpse of a detainee.
The exploration team was referenced in the 2011 game Star Wars: The Old Republic from BioWare through the Crew Skill quest called "The Forgotten Prison." A prior iteration of this quest was only available to players aligned with the Sith Empire, identifying the team as Imperial; however, this detail, along with information about what happened during the mission, was later taken out of the game.