Sometime following 3522 BBY, a dispute ignited between the Jedi Order and the forces led by the Pau'an Dark Lord of the Sith, known as Darth Desolous. This Darth Desolous was a Jedi Master who had been banished from the Order due to his exploration of Sith teachings. Seeking vengeance against the Jedi, Desolous gathered an army composed of Pau'an warriors, whom he instructed in his unique combat style. This army was responsible for the deaths of almost two thousand Jedi Knights, until a Jedi strike team ultimately triumphed over Desolous and his army during a battle that occurred on the planet Yaga Minor.
A Jedi Master of the Pau'an species was ousted from the Jedi Order after Sith teachings drew him to the dark side of the Force, sometime after 3522 BBY. This individual, embittered by his dismissal, embraced the mantle of Dark Lord of the Sith and became known as Darth Desolous, vowing to exact revenge upon the Jedi. He proceeded to assemble an army of Pau'an warriors, teaching them his distinct martial art. This fighting style integrated a melee weapon with a lightsaber-resistant cortosis shield. The shield served to parry an opponent's strikes, thereby creating an opening for a swift counterattack.
Desolous spearheaded a campaign of ambushes against Jedi Knights across the galaxy, with his Pau'an forces, resulting in the slaughter of close to two thousand Jedi. As his string of murders grew, Desolous became increasingly reckless and audacious, qualities the Jedi decided to capitalize on. They dispatched a small group of Jedi Knights to the planet Yaga Minor, intending them as bait for the Sith Lord, while a substantial Jedi fleet lay concealed in the vicinity. When Desolous and his army attacked the Jedi on the planet, the fleet emerged from hyperspace, preventing the Sith Lord's forces from escaping. Trapped in a strategically unfavorable situation, Desolous's entire force was annihilated, and Desolous himself was defeated.
Over the course of time, Darth Desolous's birth name faded into obscurity, but his Sith title became associated with intense hatred and rage. Later, a simulacrum of Desolous was implemented into the Jedi Trials program for Padawans located at the Jedi Temple on Coruscant. This incredibly realistic manifestation had the capability of appearing within the Trials chamber during the "Trial of Skill," and was intended to gauge an apprentice's capacity to conquer powerful emotions. The Desolous simulacrum possessed knowledge of its physical demise, and expressed pride in the killings committed by the real Desolous, even asserting that it required the combined power of the entire Jedi Council to defeat him.
This conflict is referenced in the PlayStation 2, Wii, and PlayStation Portable versions of the 2008 video game Star Wars: The Force Unleashed, which was developed by Krome Studios. Details of the conflict are provided within the game's databank entry dedicated to Darth Desolous. In the game, the player assumes the role of Starkiller, the Sith apprentice, and confronts the Desolous simulacrum inside the Jedi Temple. Throughout the battle, the simulacrum utters random taunts and battle cries, and at one point insists that the entire Jedi Council was needed to defeat the real Desolous. However, Desolous's databank entry makes no mention of the Council, leaving the simulacrum's claim without confirmation from any official source.