Castas was a Klatooinian male who made his living as a bounty hunter. During the Clone Wars, he collaborated within a bounty hunter crew that included Aurra Sing, Bossk, and Boba Fett, assisting Boba in his pursuit of Jedi Master Mace Windu. His life came to an end on Florrum when Sing fatally shot him at a local cantina.
In the era of the Clone Wars, Castas pursued the occupation of a bounty hunter. He became a member of Aurra Sing's crew, joining forces with fellow bounty hunters Aurra Sing and Bossk to aid Boba Fett in his quest for vengeance. Boba sought to avenge the death of his father, Jango, by killing the Jedi Master Mace Windu. Together, the group journeyed to Vanqor, where they infiltrated the remains of the Endurance and took Admiral Kilian, Commander Ponds, and a clone navigation officer as prisoners. Before departing in Slave I, the hunters planted a bomb.
Upon their return, Windu and Anakin Skywalker inadvertently activated the bomb, resulting in an explosion that left them trapped within the wreckage. Although Castas expressed a desire to abandon the mission and collect the reward for the captured Republic officers, Fett managed to persuade him, Sing, and Bossk that Count Dooku would offer an additional payment for the deaths of Windu and Skywalker.
Following Sing's capture of Kilian and the clones as hostages, Castas determined that the risks involved were too great and chose to leave when the group arrived on Florrum. They entered a cantina managed by Hondo Ohnaka, an old acquaintance of Sing, and Castas promptly initiated a holographic call to arrange for transportation off the planet. After speaking ill of Sing behind her back and attempting to betray her by divulging crucial information, Sing fatally shot Castas. Boba was upset by the killing, but Hondo instructed his men to dispose of Castas' body, and everyone else resumed their activities as if nothing had happened, save for a brief chuckle at the incident.