K-3PX was a blue-black 3PX-series protocol droid. The droid was in the service of Darth Vader, who used it as an espionage droid and stationed it on Gamandar. While there, it was approached by Lando Calrissian, Chewbacca, C-3PO, and R2-D2 who believed its master was Tay Vanis, and that it held information about the second Death Star. In truth, Vanis's droid was Ellie.