Darth Desolous, born circa 3,522 BBY, was a male Pau'an Jedi Master prior to becoming a Sith Lord. After he studied Sith teachings and fell to the dark side of the Force, he was expelled from the Jedi Order.
As the new Dark Lord of the Sith, Desolous swore revenge on the Jedi and assembled an army of Pau'ans, whom he trained in martial arts and used in his fight against the Order.
Desolous and his men slew almost two thousand Jedi, until they were crushed by the Jedi Order during a battle on the planet Yaga Minor. During the battle, Desolous was killed. A simulacrum of Darth Desolous was later incorporated into the Jedi Temple's Trial of Skill program. In 3 BBY, the program activated itself and fought Sith Lord Darth Vader's secret apprentice, Starkiller, and was defeated by him.
Desolous is a minor villain in Star Wars: The Force Unleashed during the downloadable mission in the Jedi Temple.