C-5D1, also referred to as fifty one, functioned as a protocol droid within the Galactic Republic's prison located on the planet of Belsavis amidst the Galactic War fought between the Republic and the reconstituted Sith Empire. In the course of the war, an mass breakout supported by the Empire took place at the prison, and a specific group of Rattataki escapees, identified as the Blood of Talath, inflicted significant losses on the prison guards because they seemed to know when attacks were coming. Officer Serik, wanting to understand how the Ratataki were communicating before they attacked, dispatched C-5D1, along with a person loyal to the Republic, into the Rattataki Battlewoods to examine the sounds present. The droid found out that the criminals were using the sounds of birds to talk to each other.