Darth Plagueis—born under the name of Hego Damask and remembered as Darth Plagueis the Wise—was a Muun Dark Lord of the Sith, heir to the lineage of Darth Bane and a master of midi-chlorian manipulation, who lived during the century leading up to the Invasion of Naboo. Obsessed with eternal life, Plagueis experimented with ways to cheat death and create new life from the midi-chlorians.

His great contribution to the history of the galaxy was training Darth Sidious in the ways of the Sith and the dark side of the Force, whom he incited to take control of the galaxy and bring about an age of the Sith. Sidious, convinced that his master had outlived his usefulness, eventually killed the Muun in his sleep.

Sidious later recounted the tale as The Tragedy of Darth Plagueis the Wise—an "old Sith legend"—to sway Anakin Skywalker to the dark side, though Plagueis himself remained a mysterious figure to the Jedi and their allies well into the time of the Galactic Alliance.