In 3643 BBY, while working as a spy for Darth Baras, Rylon led Republic forces to engage the Empire on the planet of Balmorra. After taking a Balmorran factory, Rylon and his troops encountered Baras' apprentice, who was sent to eliminate Rylon as he was in danger of being compromised. After watching his squad die, Rylon came face-to-face with the Sith Warrior. Rylon expressed his profound loyalty for the Empire and prepared himself for combat with the Sith, but the Sith Warrior killed Rylon in combat.
Rylon had a son, Durmat, who was also killed by Baras' apprentice as he was aware of his father's true allegiance.
After Rylon's death, Jedi Knight Mashallon recorded the conversation and attempted to warn the Jedi Council and Jedi Master Nomen Karr that the Sith were after Nomen's apprentice by transmitting her findings. However, the recording was intercepted by Lieutenant Malavai Quinn, causing Mashallon to fail in her mission.
- Star Wars: The Old Republic (First appearance)