Onyx, identified as a Zygerrian male, operated as a slave merchant and commanded a vessel used for slave trading. In the era of the Clone Wars, his path crossed with a Jedi team comprised of Anakin Skywalker, Obi-Wan Kenobi, and Ahsoka Tano, who were actively investigating the disappearance of Kiros' inhabitants. Following the Jedi's surreptitious entry onto his vessel, Onyx managed to seize Ahsoka, suggesting an exchange involving her for the release of his crew members, who were being held by Skywalker and Kenobi. His true intention, however, was to kill the Jedi by unleashing a giant creature. This plan failed when the creature was defeated, enabling the Jedi to gain full access to the ship through the rear air dock, which Ahsoka had opened. In a moment of self-preservation, Onyx divulged all the information he possessed regarding the Kiros slaves. Subsequently, he and his crew were taken into custody aboard the Jedi's vessel.