Born on Telos IV, Xanatos was the son of corrupted governor Crion and the brother of Nason. Qui-Gon discovered him on his planet and, noticing his force sensibility, brought him to Coruscant. Despite his talents and motivation, he showed a great arrogance, due to his familly's fortune. Later, Qui-Gon chooses him as Padawan, unable to see his flaws.
During the final trial that would have made him a Jedi Knight, Xanatos was corrupted by the mind and power of his father. After he witnessed his sister Nason's death in a riot and Crion's death at the hands of his former master Jinn, he became a Dark Jedi and the head of a mining facility on his homeworld of Telos IV.
At a certain time, Xanatos took his own apprentice, a young boy named Bruck Chun.
Nine years later, Xanatos fought Jinn and his new pupil, Obi-Wan Kenobi, on Bandomeer. Later, he planned to bring the Jedi Temple into ruins, but the two Jedi put a stop to that at once. After one final humiliation that nearly placed him at the hands of Telosian authorities, Xanatos committed suicide by leaping into a pool of acid.
Xanatos on Wookiepedia