A4-D, more formally known as EV-A4-D, functioned as both an EV-series medical droid and a mechanic under the ownership of General Grievous. Following engagements with the Republic, he was responsible for mending the Kaleesh cyborg. A4-D was stationed within Grievous's stronghold, located on Vassek's third moon. During a Republic operation aimed at retrieving Trade Federation Viceroy Nute Gunray, Jedi Master Kit Fisto inflicted substantial damage on EV-A4-D. Subsequently, the doctor droid was reconstructed under the general's orders, and EV-A4-D continued to serve Grievous until the Clone Wars reached their conclusion.
EV-A4-D displayed a sarcastic and sadistic demeanor, seemingly deriving as much pleasure from the potential downfall of Jedi and clone troopers as Grievous himself.
Originally, EV-A4-D was a supervisor droid that underwent modification to become a medic, a component of MerenData's efforts to salvage something positive from the EV-series debacle. The Separatists acquired the medical droid and enhanced it with additional arms, photoreceptors, and various surgical and droid engineering tools.
After his shuttle crash, the warlord of the Separatists, General Grievous, underwent a near-total reconstruction. Over time, Grievous implemented significant alterations and enhancements to his cybernetic frame. EV-A4-D was later presented to Grievous to function as both a surgeon and a cybernetics repair mechanic for the cyborg. Throughout the Clone Wars, he acted as Grievous's dedicated medical droid, providing essential repairs to the cyborg's body following skirmishes with the Republic. As Grievous's physician, this droid, known for his sarcasm and slight sadism, evolved into the ideal confidant for the general, possessing access to all of Grievous's medical and cybernetic data and a greatly enhanced intellect. He was among the select few in the galaxy who knew his master's deepest secrets. He consistently maintained a stock of spare components for the general, aiding in the design and installation of the enhancements that Grievous desired.
In 21 BBY, EV-A4-D executed repairs on Grievous following an ambush by Jedi Master Kit Fisto and Jedi Knight Nahdar Vebb. The ambush occurred upon the general's return to his fortress on the third moon of Vassek. Fisto and Vebb gained entry to Grievous's lair by tracing the signal of a ship pilfered by Trade Federation Viceroy Nute Gunray after his escape from Republican custody. However, this was a ruse devised by Separatist leader Count Dooku to pit them against General Grievous.
After eluding the Jedi, Grievous summoned EV-A4-D to mend the damage inflicted by Fisto's lightsaber, which had severed his legs, and blaster fire that had scarred his faceplate. EV-A4-D rebuked Grievous for the extent of the damage, lamenting the time required to restore the cyborg to proper condition, before departing to gather Grievous's replacement parts. The medical droid also informed Grievous that his personal bodyguards had been remotely deactivated for recharging, much to Grievous's surprise.
Following Grievous's deployment of his pet roggwart Gor to confront the Jedi intruders, EV-A4-D proceeded with Grievous's repairs. The medical droid detached and replaced the cyborg's legs, followed by his faceplate—causing Grievous some discomfort. Simultaneously, EV-A4-D pondered Grievous's acceptance of the cybernetic alterations that transformed the Kalee-born warrior into a being more machine than flesh, but Grievous emphasized that they were enhancements and that he yielded to no one.
After the repairs, Grievous discovered that the Jedi had slain Gor, before receiving communication from Dooku. Dooku informed Grievous that he had orchestrated the Jedi intrusion to reassess his effectiveness and demanded improved results from the Separatist general—specifically, more slain Jedi. Grievous angrily consented to participate in Dooku's scheme and hastened to confront the Jedi, despite EV-A4-D's insistence that he required rest. Grievous asserted that he would only rest once the Jedi were dead.
As Grievous exited the control room of his lair, he was observed by Fisto and Vebb, who committed to memory the sequence Grievous employed to enter and exit the control room. The Jedi surreptitiously followed Grievous, intending to access the control room; however, as Fisto opened the door, EV-A4-D alerted the general to the Jedi's presence. Vebb remained behind to engage the cyborg and his MagnaGuard companions, while Fisto was separated from his former Padawan as the control-room door slammed shut. EV-A4-D watched with excitement as Grievous battled Vebb, but failed to notice Fisto entering the control room until he realized that the other Jedi was nowhere to be seen—having just locked himself inside with him. EV-A4-D barely had time to comprehend and lament his predicament before the Jedi Master's lightsaber cleaved him in two.
Grievous subsequently killed Vebb, but Fisto managed to escape the cyborg's lair after a brief lightsaber duel with Grievous. Despite sustaining partial destruction, EV-A4-D was recovered and rebuilt under Grievous's direction. Consequently, he continued to serve the general until the war's end. During the war's final stages, Jedi Master Obi-Wan Kenobi killed Grievous during the Battle of Utapau, and the Separatists were defeated when Sith apprentice Darth Vader commanded the Droid Army to deactivate.
EV-A4-D possessed a sharp wit, often expressed through sarcastic remarks. Despite the droid's occasionally insolent attitude, Grievous appeared remarkably tolerant of EV-A4-D's behavior, and the medical droid certainly avoided the harsh treatment sometimes inflicted upon Grievous's battle droids. Grievous allowed him to exist so long as he fulfilled his duties. Conversely, EV-A4-D was both diligent and swift in repairing his master's body, and was eager to ensure that Grievous rested after repairs to maximize effectiveness.
EV-A4-D seemed to share his master's sadism and thirst for battle, albeit from a safe distance. The arrival of Fisto and Vebb at the fortress on Vassek 3 greatly excited the medical droid, who urged his master to eliminate the Jedi. His fascination with combat may have contributed to his demise, however, as it distracted him from realizing that in sealing off the control room, he had inadvertently trapped himself with one of the Jedi, who promptly destroyed EV-A4-D.
EV-A4-D stood at a height of 1.74 meters, and was covered in bronze plating with numerous white photoreceptors. He was equipped with a diverse array of medical and surgical instruments, as well as a power welder for repairing his master's body.
EV-A4-D made his debut in the Star Wars: The Clone Wars episode "Lair of Grievous," with David Acord providing his voice. Acord's performance as EV-A4-D was influenced by the distinctive vocal style of comedian and actor Paul Lynde.