MB-13A, alternatively known as MB-13, functioned as a BB-series astromech droid for the First Order during their control of the Colossus. After an altercation with CB-23, this droid plummeted down an elevator shaft. Miraculously, it survived this fall and, following the Colossus' departure from Castilon, managed to reach engineering, where its presence terrified the Chelidae staff, causing them to retreat into their shells. When CB-23, Kazuda Xiono, Neeku Vozo, and Torra Doza descended to repair the station's malfunctioning gravity generator and communications systems after an exit from hyperspace, MB-13A bided its time, waiting for them to complete the repairs before disabling CB-23 and Vozo. Once Xiono and Doza realized the droid was active, it pursued them into the engineering room, forcing them into hiding, as it attempted to transmit a signal back to the First Order. Xiono and Doza ultimately thwarted its plan, ejecting the droid into space and thus ending its threat to the Colossus.
During the occupation of the Colossus platform on Castilon towards the close of the New Republic era, MB-13A was part of the First Order forces. When Kazuda Xiono, a Resistance operative, disguised himself as a stormtrooper, specifically CS-515, and absconded with a data rod from an Upsilon-class command shuttle, MB-13A confronted and engaged the imposter. However, Xiono proved superior, tearing off the droid's head. Despite this damage, MB-13A's body continued to function. Xiono discarded the droid's head before being escorted away by Sergeant CS-812.
Subsequently, MB-13A was seen patrolling Aunt Z's Tavern, carefully watching for any indications of rebellion or disloyalty. When Grevel, an Aleena, inadvertently bumped into the droid, MB-13A responded by activating its electro-shock prod. The droid later used the prod on Glitch, Aunt Z's service droid, causing him to move away. Following the placement of a propaganda poster in the tavern by two stormtroopers, MB-13A followed them as they left.
Later on, MB-13A was monitoring the patrons of Aunt Z's Tavern following Captain Imanuel Doza's choice to suspend races in the Colossus under the orders of Commander Pyre. The droid listened to a discussion between Kaz and his companions Neeku Vozo and Tamara Ryvora, the latter of whom showed sympathy for the First Order's presence. Soon after, their friend Torra Doza arrived with news of the disappearance of Ace Squadron leader Hype Fazon.
MB-13A alerted two stormtroopers, who attempted to reassure Torra and her friends that Hype had been granted permission to leave the planet. In reality, he had been apprehended by the First Order. MB-13A was present when Aunt Z angrily condemned the First Order and ejected their poster. She was then arrested and sent to the West Docks for deportation.
Later, while carrying refreshments through the Colossus, MB-13A was ambushed by the Resistance BB-unit CB-23, who then impersonated it to deliver a message to Captain Imanuel Doza about Kaz's scheme to sabotage the Colossus in order to send a transmission to the Resistance.
During a patrol, MB-13A stumbled upon Kaz and his allies Torra Doza and CB-23, who had started a small resistance cell. Kaz and his group attempted to hide under a trapdoor, but MB-13A revealed their location and sounded the alarm. CB-23 attacked MB-13A and fought with the First Order droid. After damaging its visual processor, she tricked it into falling down an elevator shaft. After the droid's disappearance, Kaz remarked that there was "only room on the Colossus for one ball droid."
Unbeknownst to Xiono, CB-23, and their companions, MB-13A had actually survived the fall down the shaft. Following the Colossus's relaunch into space and escape from Castilon, the droid navigated its way to the engineering sections of the space station. The Chelidae engineering crew, upon discovering the droid's presence and the danger it posed, retreated into their shells to protect themselves. After the Colossus exited hyperspace, it experienced a series of mechanical failures, including the long-range communications and the gravity generator, prompting Xiono, Torra, CB-23, and Neeku Vozo to venture down to engineering and the hyperdrive chamber to address the issues.
Upon entering engineering, Xiono and his group found the Chelidae inside their shells, and, unaware of MB-13A's presence, assumed they had been frightened by the station's flight. They began to repair the communications and gravity, not knowing that the enemy droid was watching them. It first disabled CB-23, after Xiono sent her to repair some systems in a separate, darkened room. Eventually, when Xiono wondered what was taking his droid so long, Vozo went after her and discovered her floating and deactivated, before he was attacked and trussed-up by the enemy droid. After the communications had been repaired, Xiono and Torra went to see why their friends hadn't returned, and found Vozo and CB-23. Vozo warned them to go, but MB-13A arrived before they could. Xiono attempted to distract the enemy droid while Torra tried to untie Vozo, but he was shocked unconscious by the droid and Torra escaped with him. After Xiono regained consciousness, the two headed for the engineering room, eventually hiding from MB-13A in the ceiling.
Xiono and Torra observed the droid preparing to send a coded transmission to the First Order, a situation that alarmed Captain Doza and Jarek Yeager on the bridge. Yeager quickly concluded that a remaining First Order infiltrator was responsible. Xiono jumped down to pull the droid away from the console to prevent it from sending its transmission to Castilon, and, after they were joined by a reactivated CB-23, Xiono and Torra opened a hatch in the floor to blow the infiltrator into space. MB-13A grabbed onto Xiono first with its grappler and later its cables in an attempt to avoid being thrown out, but Torra managed to close the hatch on the cable, which severed it, sending MB-13A drifting into space and saving Xiono's life.
MB-13A, a black BB-series astromech droid, was designed to serve the First Order. Its duties encompassed guarding First Order communications, monitoring the public for any signs of disloyalty or dissent, delivering refreshments, and patrolling the corridors of the Colossus. The droid displayed hostility toward both civilians and Resistance members. MB-13A frequently used its electro-shock prod to intimidate other droids and civilians. Although MB-13A was capable of putting up a fight, it was ultimately outmatched by both Kazuda Xiono and CB-23.
MB-13A made its debut in "The New Trooper," an episode from Season 1 of Star Wars Resistance. The "MB" in its designation stands for "Murder Ball," a nickname given to it by the production crew.