R4-K5 was a type of astromech droid from the R-series, serving alongside Darth Vader, the Sith Lord who was once the Jedi Knight Anakin Skywalker, on missions for the Galactic Empire in the early years of the Imperial Era. This droid, originally owned by a Jedi, was picked by Vader because of its somber hue to take the place of his previous astromech droid, R2-D2.
During missions to the planets of Murkhana and Ostor, R4-K5 occupied the droid socket located in Vader's customized Eta-2 interceptor. Although the droid was capable, it never developed the same close relationship with its Sith master that R2-D2 had with Skywalker; Vader viewed R4-K5 as merely a piece of equipment.
R4-K5, an astromech droid belonging to the R-series, once belonged to a member of the Jedi Order. In the year 19 BBY, Anakin Skywalker, having recently become the Sith Lord Darth Vader, suffered serious injuries during a duel with his former Master, Obi-Wan Kenobi, on the world of Mustafar, located in the Outer Rim. After being forced to wear a black suit of armor, Vader also obtained a black Eta-2 Actis-class interceptor during the initial days of the Imperial Period. Vader selected R4-K5 as his new astromech droid to replace Skywalker's astromech R2-D2, because the Sith Lord considered its dull exterior to be representative of his own inner darkness.
R4-K5 was stationed on the new Imperial Star Destroyer known as the Exactor, specifically in the vessel's third launching bay, along with Vader's interceptor. More than two weeks after the establishment of the Galactic Empire, the droid was in the astromech socket of the Sith Lord's interceptor during an attack targeting the fugitive Jedi Knights Roan Shryne and Olee Starstone, as they attempted to escape from the Outer Rim world of Murkhana, which had previously been aligned with the Separatists. R4-K5 was vital in helping Vader understand the tactical situation, providing him with details about the escape plan involving the CloakShape fighter used by the Jedi, and alerting him to their impending departure using a hyperdrive ring. Despite the droid's assistance, Vader was unable to eliminate his targets before they escaped beyond the range of his interceptor.
Several months later, R4-K5 accompanied Vader in Green Squadron during the second part of the Shrouded Offensive, a large-scale campaign against a Separatist holdout on the planet Ostor that ultimately failed. Vader, under orders from Emperor Palpatine to initiate a direct aerial assault following the failure of an initial ground assault, led the squadron in an attack on a shielded city and engaged in a dogfight with V-19 Torrent fighters flown by followers of the rogue clone trooper Kaddak. During the battle, Imperial clone pilot Hock Malsuum realized that the squadron's departure had left the Star Destroyer from which they launched vulnerable, prompting Vader and R4-K5 to turn back and defend it. The battle concluded with a pyrrhic victory for the Empire.
R4-K5 had a round silver dome with black tool panels and a sensor, along with a red status light. The droid's plating was a dark-gray color, complemented by black tool coverings. As a class two droid made by Industrial Automaton, R4-K5's height was 0.96 meters. Moreover, R4-K5 could interface with the systems of the Eta-2 Actis-class interceptor and analyze potential targets like skiffs and hyperdrive rings, sending this information to the interceptor's cockpit displays when requested by the pilot. R4-K5 did not have the same close relationship that Skywalker had with his former astromech, R2-D2; Vader simply considered the droid another piece of equipment.
R4-K5 was first featured in the novel Dark Lord: The Rise of Darth Vader, written by James Luceno and released in 2005. Although not identified by designation, R4-K5 is initially described as an astromech with a black dome, and is mentioned two more times as "the astromech." The R4-K5 designation was provided by Hasbro in 2006 in conjunction with an action figure based on the droid.
The droid later made a brief appearance in the 2008 non-canon Soulcalibur IV tie-in comic book Star Wars: Visions of the Blade, where R4-K5 is seen in a single panel connected to Vader's interceptor. The droid accompanies the Sith Lord to a planet located in the Cowl Crucible nebula, where Vader encounters the Soulcalibur character Mitsurugi. In the comic arc Star Wars: Darth Vader and the Lost Command, Vader's heavily modified interceptor is shown with an astromech droid; however, its appearance is inconsistent across panels, and it is not confirmed to be R4-K5.
The color scheme of R4-K5 is inconsistent across various sources. In the 2005 reference book The New Essential Chronology, where the droid was first depicted, R4-K5 has a black dome and a white body. Later, several Hasbro figures of the droid show R4-K5 with a dark-gray body, a silver dome, and black panels, or alternatively with a purple body. In the comic Darth Vader and the Cry of Shadows 4, R4-K5 is depicted with a black body and silver tool panels. This article considers the version of R4-K5 shown in the StarWars.com Databank to be the accurate representation.