|“||The war is over. The Republic has won. If we keep fighting, you will destroy us. I accept this. Darth Arho does not. He is a member of the Dark Council, but he is a thug. The Council needs someone more...progressive...if the empire is to survive.||„|
|~ Darth Malgus on Darth Arho|
He serves as one of the two secondary antagonists of the Ilum storyline, alongside Admiral Shai, in Star Wars: The Old Republic.
During the Cold War, Darth Arho ascended to the Dark Council and became head of the Sphere of Military Offense after the death of Darth Baras; who was killed by The Emperor's Wrath. Following this, he later traveled to Ilum with the single goal of obliterating all the Jedi and Republic troopers on the planet. Following the defeat of the Sith Emperor at the hands of the Hero of Tython, Arho, determined to avenge his fallen master, pushed even harder for the final defeat of the Republic.
Darth Arho stayed away from the powerplays of other Dark Councilors and his warlike personality was often used by Councilors against one another. He proved himself on Ilum to be a capable commander, however, the Dark Council disapproved of his willingness to win at all costs. When Darth Malgus declared himself the new Sith Emperor, and also launched an invasion on Ilum, Darth Arho was part of the Dark Council strikeforce sent to defeat Malgus.
After a sustained battle, with both the Republic and Malgus, Darth Arho was forced into the heart of the planet by the Repulic forces. In his final confrontation with the Republic Arho had three Sith to back him up. However, he killed one of these Sith by choking him as a show of power. After a fierce battle, Darth Arho was defeated and killed by the combined forces of the Republic.