R-K77 functioned as a protocol droid in the office of Mon Mothma, the Chancellor of the New Republic, on Chandrila, a planet she called home. Following the Galactic Empire's attack on Mon Mothma and other prominent New Republic figures during the Republic's Liberation Day celebrations in 5 ABY, R-K77 communicated an immediate request for a meeting from Senator Leia Organa to the Chancellor. Upon R-K77's notification to Mothma that Senator Organa had indicated the meeting was a code K-one-zero, a designation employed by the Rebel Alliance signifying "disengage and regroup," the Chancellor instructed the droid to relay to Organa that she was immediately departing to meet her. R-K77 possessed a metallic visage finished with a matte white enamel, and her speech was characterized by a distinct Chandrilan inflection.
The character of R-K77 was featured in Aftermath: Empire's End, a novel penned by Chuck Wendig in 2017.