6G-66, also known as "Sixer," functioned as an astromech droid for the Resistance throughout their war against the First Order. During Black Squadron's mission to recruit allies and integrate new systems into the Resistance, 6G-66 served as the astromech aboard Jessika Pava's T-70 X-wing starfighter. Despite Pava's acknowledgement that Sixer was not particularly enthusiastic about the assignment, given her reputation as the "Great Destroyer" among the astromechs at the Resistance base located on D'Qar, she insisted that having an astromech onboard was essential for such a critical mission.