R5-K6 was an R5 unit that served in the Alliance to Restore the Republic’s Red Squadron during the Galactic Civil War against the Galactic Empire. Based on the moon Yavin 4, the droid was part of the forces scrambled to engage the Empire in the Scarif system while a Rebel strike team attempted to steal the Death Star plans on the planet Scarif below. R5-K6 flew with Red Leader Garven Dreis in a T-65B X-wing starfighter and engaged enemies starships in space while the strike team successfully stole the plans, after which R5-K6 and Dreis retreated.
Shortly after the plans were stolen, the Empire’s Death Star superweapon traveled to the Yavin system to destroy the Rebel base and Yavin 4 entirely. R5-K6 once again flew with Dreis as part of the forces that attacked the Death Star, engaging enemy starfighters while the BTL-A4 Y-wing assault starfighter/bombers of Gold Squadron attempted to exploit the vulnerable thermal exhaust port that the Alliance had learned about from the Death Star plans. After Gold Squadron were mostly destroyed, R5-K6 and Dreis made an attack run on the port themselves, but failed to hit their target, after which the pair were killed when the Sith Lord Darth Vader destroyed their X-wing starfighter.