C-21 Highsinger was a combat droid bounty hunter that operated during the Clone Wars. He was part of Krayt's Claw, a syndicate of bounty hunters that included Boba Fett, Latts Razzi, Dengar, Bossk, and Oked. He had extensive modifications, including precision-engineered servomotors and manipulators. Although a deadly combat droid, C-21 Highsinger had his battle programming pushed beyond its limits when defending Otua Blank's subtram from the swift Kage Warriors.
C-21 Highsinger was a droid bounty hunter active in the galaxy. Around 33 BBY, Highsinger joined the hunt for fellow bounty hunters Jango Fett and Aurra Sing. In the end, Fett defeated their pursuers with a missile from his jetpack, with the blast severing Highsinger's arm. Highsinger claimed his severed limb and sat amidst the flames.
During the Clone Wars, Highsinger joined Krayt's Claw, the group of bounty hunters put together by Jango's son Boba Fett in order to undertake a mission on the planet of Quarzite. The hunters were joined by Asajj Ventress—although they were unaware of her identity—after she killed one of the members of their team. The group was tasked with guarding a large wooden chest aboard a subtram, which was to be delivered to the Belugan Otua Blank. As the hunters spread out in anticipation of a confrontation, Highsinger was stationed near the cargo. Though the trip began easily enough, soon the tram was beset by Kage Warriors, who sought the cargo for themselves.
Highsinger and the crew on Quarzite
One by one, the hunters fell. Though Highsinger was one of the last hunters standing, the Kage Warriors' leader, Krismo Sodi, was able to dispatch the droid by linking him with fellow hunter Latts Razzi as she was thrown from the train. Highsinger fell beside Razzi, though both survived. In his absence, Fett too was bested by Sodi, who soon revealed that the cargo was his sister, Pluma Sodi, who was to be forcibly wed to Blank. Ventress, having suffered many changes in her recent past, ended up placing Fett within the chest and delivering him to Blank, collecting both a bounty from the warlord as well as from the Kage Warriors for freeing Pluma. She then shared the first bounty with Highsinger and the others, telling them that Fett would join them soon enough before departing.
In the second year of the Clone Wars, Highsinger and several other members of Krayt's Claw including Fett, Razzi, and Embo were frequenting a bar in Coruscant's Level 1313 when they were visited by the undercover Jedi Master Quinlan Vos. Vos had been dispatched by the Jedi High Council on a mission to assassinate the Separatist leader Count Dooku and had been partnered up with Asajj Ventress, a Dathomirian Nightsister who had once been Dooku's Sith apprentice. Fett informed Vos that Ventress was hunting a Volpai fugitive named Moregi on Pantora. Vos traveled to Pantora where he managed to partner up as a bounty hunter before revealing his true identity and enlisting Ventress' support to kill Dooku.
Following the failure of Vos and Ventress' assassination attempt, Ventress came to enlist the aid of Krayt's Claw. Fett was visited by her at Chalmun's Spaceport Cantina on Tatooine by Ventress, who wanted to rescue her partner and lover from Dooku, offering them a significant sum of credits to help her. They agreed, and Highsinger and the other Krayt's Claw members traveled on Fett's starship Slave I to Serenno on a mission to infiltrate Castle Serenno and rescue Vetnress' partner. While Ventress infiltrated Dooku's palace, Highsinger and his associates staged a diversion and attack several Separatist vehicles and droids. They even managed to snare Dooku under some webbing but were forced to flee when Vos spurned Ventress' rescue and openly sided with Dooku.
During the Galactic Civil War, Highsinger was among the bounty hunters hired by Darth Vader to return Doctor Aphra to him, after she was captured by the Rebel Alliance on Vrogas Vas.
Being unable to speak Galactic Basic Standard, Highsinger was not a frequent conversationalist, and often only spoke when addressed directly. He was a straightforward operator, focusing on the job at hand. His torso was rotatable at the pelvic mount, which allowed him to perform rapid blaster attacks to eliminate multiple opponents within a circular area around him. Combined with his advanced servomotors, this made Highsinger a formidable combatant in close-quarters, even able to hold his own against skilled organic humanoids like the Kage Warriors.
Before the cancellation of the Star Wars: The Clone Wars television series, Highsinger was set to make an appearance during a four-episode arc starring Boba Fett and Cad Bane. In a clip revealed during the Animated Origins and Unexpected Fates panel at Celebration Orlando in 2017, Highsinger was seen siding with Cad Bane during a stand-off against Boba Fett and other bounty hunters, restraining two hostages.