Around 19 BBY, Clone X was dispatched by Vice Admiral Rampart to help cover up knowledge of the attack on Kamino and genocide of its population, in order to pass the Imperial Defense Recruitment Bill. As part of this, he tracked clone trooperCade, who had threatened to tell the Imperial Senate the truth about the fall of Tipoca City if Rampart did not do so himself. He killed Cade outside 79’scantina on Coruscant, but failed to kill fellow trooper Slip, who managed to escape on a speeder bike.
Clone X was then contacted by Rampart, who asked if he had located Slip. While he had been unable to, he had noticed that Pantoran guards had been searching for him too. Rampart ordered him to follow Senator Riyo Chuchi, in hopes that she would lead him to Slip. Rampart ordered him to eliminate anyone who potentially had knowledge of the conspiracy, including the senator herself.
The assassin successfully followed Chuchi to a rendezvous point, at which Slip was expecting to meet with Rex. He shot and killed Slip and one of the senator’s guards. A standoff ensued and the remaining guard was able to hold off the assassin while the senator tried to make her escape. The assassin gave chase into a warehouse filled with smoke, where he killed the remaining guard, but was stunned by Rex, who had got to the rendezvous too late but followed the sound of blaster fire and was able to save Chuchi.
Clone X awoke to find that Rex had brought him to Trace Martez’s repair shop, in the level 1313 of the Coruscant Underworld. Rex questioned him and he proved uncooperative, surprising Rex with knowledge of his name and telling him he was fighting the wrong battle. After referring to himself as «a believer,» he took his own life via a suicide shocker, which killed him instantly.
His body was then transferred to a hoversled and shown to Clone Force 99, with Rex mentioning that his identifying number had been wiped.