A protocol droid identified as D-4 was in the service of Countess Anya. Later, the droid served Anya's husband, Gora, and her son, Ramil. When Abyssin pirates launched an invasion of Serenno, Jenza dispatched the droid to Coruscant with instructions to locate Dooku and request assistance in saving their people. Upon their arrival at Serenno, the pirates launched an assault on their vessel, resulting in a crash landing on the planet. D-4 sustained irreparable damage during the crash.
Prior to 90 BBY, D-4 had been a member of House Serenno for a period of time, and she went with Count Gora, Countess Anya, along with their children, Ramil and Jenza, to a celebratory festival that was being held in the planetary capital of Carannia. This celebration was intended to provide planets from the Outer Rim with an opportunity to display what they could offer to the Galactic Republic. D-4 was quick to emphasize the potential benefits this event could bring to Serenno when Gora began to complain about it. Anya, wanting to prevent a conflict between the Count and the protocol droid, instructed D-4 to accompany the children as they explored the festival, which forced D-4 to chase after them. Nevertheless, D-4 was unable to maintain oversight of her charges and, after a lightsaber demonstration, she lost sight of them within the crowd. This event led to Jenza encountering her long-separated brother, the Jedi initiate Dooku.
Several years later, specifically in 82 BBY, D-4 was present at Anya's funeral on the moon of Mantero along with the rest of the family. During this event, she was a witness to a significant protest by the citizens of Serenno who were demonstrating against Gora's leadership, as well as a confrontation between Gora and Dooku, who had attended at Jenza's invitation.
Throughout the remainder of Gora's time as count, D-4 continued to serve him. However, during Ramil's reign, in 42 BBY, Abyssin invaders attacked Serenno. As a direct response, Jenza arranged for D-4 to be smuggled off-world aboard a Vandyne freighter and transported to Coruscant, where the droid met with Dooku, who had by this time attained the rank of Jedi Master. Jenza used D-4's holotransmitter to urgently request her brother's help to rescue Serenno, and Dooku responded by bringing D-4 before the Jedi Council to request their assistance. Regrettably, because Ramil had failed to remit taxes to the Republic, the Senate had determined that the situation was not within the Republic's purview, and the Jedi consequently declined to grant Dooku's request.
Despite this setback, Dooku made the decision to return to Serenno independently. Accompanied by his longtime friends, Jedi Master Lene Kostana and her former apprentice Sifo-Dyas, Dooku and D-4 journeyed back to the besieged planet. However, upon their arrival, they were ambushed by Abyssin orb fighters. During the resulting engagement, their ship sustained multiple hits, compelling Dooku to execute a crash landing on the planet's surface. During the crash, D-4 suffered critical damage. After inquiring with Dooku if they had successfully reached their destination, the droid ceased functioning permanently.
D-4 made an appearance in the audiobook Dooku: Jedi Lost, which was authored by Cavan Scott and released in 2019.