D4-R4B, alternatively known as "Arforb," was a cantankerous R4 astromech droid who served the Alliance to Restore the Republic. This astromech droid was stationed at the Great Temple located on the moon of Yavin 4. It excelled in ground-based repair duties as a way to make up for a programming error that caused it to be afraid of flight, thus preventing it from being assigned to starfighter missions. During 1 BBY, the droid was present in one of the temple's hangars on multiple occasions when the criminal Jyn Erso passed through the area.
D4-R4B, whose nickname was "Arforb," was an R4 astromech droid in service to the Massassi Group of the Alliance to Restore the Republic. It was based within the Great Temple on the moon of Yavin 4. As one of many R-series astromech droids manufactured by Industrial Automaton within the base's droid workforce, D4-R4B suffered from a programming flaw that resulted in a fear of flying. Consequently, the droid was not assigned to starfighter roles, but instead, performed exceptionally well in ground maintenance to compensate for this limitation.
In 1 BBY, D4-R4B was positioned in one of the Great Temple's hangars at a time when the criminal Jyn Erso was being escorted through the space by a member of the Alliance's military police. Shortly afterward, the R4 unit was standing alongside fellow astromech R2-BHD near a T-65 X-wing starfighter inside the hangar when Erso was guided back through by Alliance Intelligence operative Captain Cassian Andor before their departed towards the moon Jedha. At a later point, D4-R4B was situated at the hangar entrance as Erso and Andor boarded the stolen Imperial cargo shuttle SW-0608 with the intention to travel to the planet Scarif.
D4-R4B possessed a grumpy disposition, an attribute that its fellow astromech R2-BHD considered to be illogical. It carried a significant amount of guilt due to the programming error that prevented it from assisting pilots in aerial combat, and therefore it compensated by performing outstanding maintenance work on the ground. D4-R4B featured white paneling accented by charcoal gray stripes and a black [sensor](/article/sensor]. The droid's color scheme was similar to that of the Imperial droid R4-M9. D4-R4B's height was 1.15 meters (equivalent to 3 feet and 9 inches).
D4-R4B was conceived for the Anthology Series film titled Rogue One: A Star Wars Story, which premiered on December 16, 2016. Before the film's debut, the droid was initially revealed in the inaugural teaser trailer for Rogue One, which was launched on April 7, 2016. The astromech's identity was first established in the reference book Star Wars: Rogue One: The Ultimate Visual Guide, authored by Pablo Hidalgo, and released concurrently with the film.