The Perilous, a vessel of the Imperial-class Star Destroyer type, functioned as the flagship for Darth Vader until its destruction during the skirmish with the Free Ryloth Movement.
As the flagship for the Sith Lord Darth Vader, who was the Sith apprentice of Sheev Palpatine, the Perilous transported Vader, Palpatine, and senator Orn Free Taa to the planet Ryloth. Cham Syndulla, who headed the Free Ryloth movement, learned from his spies—Vader suspected these spies were within Taa's close circle—that Vader and the Emperor would travel to Ryloth aboard the Perilous.
The prospect of assassinating the Empire's leaders—the Emperor and his top lieutenant—drove Cham to dedicate all available resources to a coordinated assault on the ship. Despite the mission's failure, the Perilous met its end in orbit above Ryloth when its hyperdrive was strategically targeted.