Cator was the guardian-protector droid of a in the Jedi Archives of the Jedi Temple. After the fall of the Jedi Order, the droid continued to keep watch and was present when Jocasta Nu returned to collect one of the items in the vault. Shortly afterward, Cator was destroyed by Darth Vader during his hunt for Nu.
Cator was a droid programmed to guard a secret vault—containing numerous artifacts and treasures—in the Archives of the Jedi Temple of Coruscant. Cator took this duty so seriously that it chose to remain hidden, rather than risk helping the Jedi during the siege of the Jedi Temple.
After the fall of the Jedi Order and the rise of the Galactic Empire, Cator still remained in the Temple standing guard alone until, eventually Jocasta Nu returned to the Temple. Cator was reunited with Nu in the secret vault, as she retrieved the list of every known Force-sensitive child in the galaxy. After retrieving the list, Nu quickly left, leaving the droid on guard once more.
Not long after, Cator attempted to deny access to Darth Vader, who had chased Nu back into the vault. Cator was soon destroyed immediately following this, but not before identifying the Sith to Nu, as the former Jedi Anakin Skywalker, with a bioscan. Cator's destruction was not in vain though, as this gave Nu time to find a powerful weapon with which to fight Vader.
Cator first appeared in the 2017 canon comic, Darth Vader (2017) 8, which was written by Charles Soule and pencilled by Giuseppe Camuncoli.