G21 was a super battle droid of the B2-series, a product of Baktoid Combat Automata. This droid fought for the Separatist Droid Army of the Confederacy of Independent Systems during the Clone Wars, in opposition to the Galactic Republic. The droid once gave a report to a commanding officer, indicating that a certain planet and its inhabitants were under control. Like other B2 super battle droids, G21 had integrated dual laser cannons as weaponry and possessed a height of 1.91 meters.
The first appearance of G21 was in the novelization of Star Wars: Episode III Revenge of the Sith, penned by Matthew Stover and published in 2005. Within the novel, G21 greeted General Grievous of the Separatists on the planet Utapau, informing him of the planet's secured status. Subsequently, The Complete Star Wars Encyclopedia, a Star Wars Legends reference work that came out in 2009, identified the droid. The reference book Ultimate Star Wars, published in 2015, confirmed that G21's name and its single quote were canon. Given that G21 was absent from the actual film and the canonicity of film novelizations is ambiguous after the 2014 declaration of all Expanded Universe content as Legends, this article refrains from making any assumptions about the canonicity of the context surrounding G21's quote.