In 1002 BBY, during the New Sith Wars, the Sith Brotherhood of Darkness fought against the Army of Light on the planet Phaseera. As the battle began, the Gloom Walkers, an elite unit in the Brotherhood of Darkness, were ordered by their Sith commanders to attempt to take out a Republic outpost in daytime. Knowing that it would be a suicide mission, the Gloom Walkers objected; however, their commander, Lieutenant Ulabore, refused to reconsider their orders.
As such, Sergeant Dessel knocked Ulabore unconscious and took command of the unit, leading the Gloom Walkers to attack the outpost during the night. They defeated the Republic forces, and Dessel's heroics throughout the battle led him to become very popular with the Gloom Walkers; however, Ulabore was furious and had him arrested for insubordination. Several of the troopers in the unit assumed that Dessel was then court-martialed and killed. The Gloom Walkers thus began to resent Ulabore for his actions, as they believed that Dessel had saved their lives and should have been hailed as a hero.
A month later, the Gloom Walkers traveled to Alaris Prime, a moon of the planet Alaris in the Kashyyyk system. They took up patrol on the moon, where they stumbled into an ambush set up by Republic forces—a mistake that one of the troopers, Lucia, knew would not have happened had Dessel still been with them. In the ensuing skirmish, the close-quarters fighting was intense and casualties were heavy on both sides. Lucia hadn't forgiven the Gloom Walkers' commander for ridding the unit of their most talented officer, and during the battle she shot Ulabore in the back from point-blank range, killing him. The skirmish lasted for just a few minutes, after which the Republic troops were forced to break ranks and flee.
The other surviving troopers of the Gloom Walkers quietly approved of Lucia's actions; they never reported her betrayal, and Ulabore was registered as having been killed in action.
Twenty-two years later, Lucia—who had become a bodyguard of Princess Serra of Doan—hired an assassin, the Huntress, to assassinate Gelba, a leader of the Doan mining caste, after the miners killed Serra's husband, Prince Gerran. Lucia compared the occurrence to her actions on Alaris Prime: Serra's husband had been killed and Gelba was responsible, so she killed Gelba, just as Dessel had been killed and Ulabore was responsible, so she had killed Ulabore. However, Lucia soon after discovered that Dessel had not actually been court-martialed and executed; rather, he had survived and become Darth Bane, a Dark Lord of the Sith.
The skirmish on Alaris Prime was mentioned in Darth Bane: Dynasty of Evil, the final novel of the Darth Bane Trilogy, written by Drew Karpyshyn and released on December 8, 2009.