Cator was a droid of the GC-8 model. Functioning as a guardian-protector, he was assigned to a clandestine vault within the Jedi Archives located in the Jedi Temple. Following the fall of the Jedi Order, the droid maintained his vigil and was present when Jocasta Nu came back to retrieve an item from the vault. Shortly thereafter, Darth Vader eliminated Cator during his pursuit of Nu.
ARO manufactured Cator, a GC-8 droid designated as both a librarian and a guardian-protector. His programming directed him to safeguard a concealed vault—filled with numerous artifacts and treasures—within the Archives of the Jedi Temple on Coruscant. Cator took his responsibility with such dedication that he chose to remain hidden, rather than risk assisting the Jedi during the siege of the Jedi Temple.
After the fall of the Jedi Order and the rise of the Galactic Empire, Cator persisted in his solitary guard duty within the Temple, until Jocasta Nu eventually returned. Cator encountered Nu again inside the secret vault, where she obtained the list of all known Force-sensitive children in the galaxy. After Nu secured the list, she promptly departed, leaving the droid to resume his watch.
Soon after, Darth Vader, pursuing Nu, attempted to gain access, but Cator tried to prevent him. Cator was quickly destroyed immediately after this, but managed to identify the Sith to Nu, using a bioscan to reveal him as the former Jedi Anakin Skywalker. Cator's sacrifice was not in vain, as it provided Nu with time to locate a powerful weapon to use against Vader.
Cator made his debut appearance in the 2017 canon comic book, Darth Vader (2017) 8, penned by Charles Soule and illustrated by Giuseppe Camuncoli.