Arcann was a Force-sensitive male Human who was the son of Senya Tirall and Tenebrae, who possessed the body of Valkorion, the «Immortal Emperor» of the Eternal Empire of Zakuul. He was the twin brother of Thexan, with whom he led a series of raids against the worlds of the larger galaxy. During the attack on Korriban Arcann was caught in an explosion that took his left arm and scarred the left side of his face; he received a cybernetic replacement. Subsequently, Arcann became furious at the indifference of Valkorion and attempted to kill him, only for Thexan to intervene and be struck down by Arcann’s lightsaber instead.

When Valkorion offered to share his power with the Outlander, Arcann attempted to assassinate Valkorion again, which was successful, killing Valkorion’s physical body while his spirit attached himself to the Outlander, whom Arcann trapped by freezing in carbonite. Arcann assumed his father’s Eternal Throne and led the Eternal Empire in a massive invasion of the larger galaxy, which prevailed over both the Sith Empire and the Galactic Republic within a year, forcing them pay tribute and making Zakuul the dominant power in the galaxy.

Arcann ruled as Emperor for five years after his father’s death, until the Outlander was rescued from carbonite and started a war against Zakuul. During the Battle of Odessen, Arcann was defeated by the Outlander and taken by his mother to recuperate, while Arcann’s sister Vaylin along with SCORPIO took over the Eternal Throne in his absence. After being healed on Voss, Arcann returned to Zakuul to aid the Outlander against his sister, joining the Alliance.