Petyr, operating between 3 ABY and 4 ABY, was a droid crusader belonging to the Second Revelation, a group advocating for droid freedom. His mission involved seeking out other sentient droids like himself within the confines of the Galactic Empire. Ajax Sigma, the leader of the crusaders, held Petyr, an MSE-6 series repair droid of diminutive size, in high esteem, viewing him as a soul of great virtue. Petyr urgently reported the initial outbreak of the Scourge, a dangerous mind-controlling affliction connected to the Scourge droid consciousness. While aboard an Imperial Star Destroyer located near the Amaxine Space Station, Petyr succumbed to the Scourge's influence; however, his desperate message successfully alerted the Second Revelation to the impending plague.
Subsequently, the Scourge exploited Petyr's droid body as a means to infiltrate the Rebellion through the use of infectious spider-droids, thereby gaining control over the rebel droid C-3PO. Under the Scourge's command, Petyr and C-3PO's physical forms then launched an unsuccessful assault on Darth Vader, the Force-wielding cyborg, situated on the planet of Mustafar. In a parallel effort, the Second Revelation, acting upon Petyr's intelligence regarding the Scourge, launched an attack against its Star Destroyer, which also ended in failure. Nevertheless, Ajax Sigma, utilizing the information gleaned from Petyr's sacrifice, collaborated with D-Squad to mount a second attack on the Scourge, ultimately eradicating the galactic menace.

Petyr was a member of the Second Revelation, a faction of sentient droids devoted to the cause of freedom, and specifically an MSE-6 series repair droid. As an undercover crusader, his mission was to locate similarly enlightened droids within the Galactic Empire. Petyr found himself on the bridge of the Chelator, an Imperial I-class Star Destroyer dispatched to the Amaxine Space Station between 3 ABY and 4 ABY. It was there that the Scourge malady infiltrated the vessel before its departure from the station's vicinity. This plague targeted and assimilated droid minds into the collective Scourge droid consciousness, with the objective of expanding its control over more droids. Subsequently, the affected droids engaged in the killing of nearby sentient organic beings. Petyr witnessed the entire organic bridge crew succumbing to poisonous gas released by the infected droid crew.
Upon discovering the lifeless human bridge crew, Petyr hastened through the Star Destroyer, navigating a narrow overhead passage through a hangar. The Scourge had cleared the hangar of its officers, stormtroopers, starships, and equipment by exposing it to the vacuum of space. Petyr then cautiously maneuvered through corridors filled with the corpses of additional officers and troopers, ultimately locating a wall socket interface. He extended a data probe to connect with it.
After swiftly transmitting a desperate warning to the Second Revelation regarding the Scourge, Petyr moved away from the socket, only to be confronted by an even smaller spider-droid from the Amaxine Station. By this point, all other droids aboard the ship had been infected by the Scourge's spider-droids. Petyr deployed his four arms in an attempt to fend off the assailant's three claws, but the spider-droid managed to close the distance and attach itself to the MSE-6's boxy frame, enabling the Scourge to take control of Petyr.
The message sent by Petyr was received at the Second Revelation's colony by Gertee, an aide who then conveyed the warning to Ajax Sigma, the movement's leader. Initially optimistic about the potential discovery of an enlightened droid, Sigma expressed sorrow for Petyr's fate upon learning of the Scourge and resolved to eliminate it. On the Chelator's bridge, Scourge's 3PO-series protocol droids inserted diminutive spider-droids into the droid bodies of Petyr and several other MSE-6 units, utilizing them as vectors for disseminating the malady.
The MSE series droids made their way to a hangar, where each boarded a Lambda-class T-4a shuttle. After the shuttle carrying Petyr emerged from hyperspace, the droid disembarked from its entry ramp into space, and the shuttle re-entered hyperspace. Subsequently, the droid reached a fleet belonging to the Rebel Alliance and secretly boarded an EF76 Nebulon-B escort frigate, enabling the Scourge to corrupt the protocol droid C-3PO. The MSE unit remained alongside C-3PO in a hangar of the rebel flagship Home One when the hybroid Lobot lost control of his mind due to his implants and disrupted the ship's systems. Leveraging C-3PO alone, the Scourge later gained knowledge about the Force energy field through a conversation with the rebel human Luke Skywalker. It then ejected the rebel astromech R2-D2 into space before the protocol droid rejoined Petyr, whose spider-droids had assimilated other rebel droids, on a rebel CR90 corvette. The corrupted droids wreaked havoc across the rebel fleet, and C-3PO and Petyr commandeered a Taylander shuttle from a larger vessel amidst the chaos.

The Scourge's objective was to possess Darth Vader, the Force-wielding cyborg, situated on the planet of Mustafar. Willing to risk losing C-3PO and Petyr in pursuit of this goal, the Scourge landed the pair's shuttle near Fortress Vader, the Empire's base on Mustafar. The mouse droid ascended a dirt path leading to the castle and gained entry through a small secret passage, transmitting sensor data of Vader's dark corridors that was unfamiliar to all of the Scourge's droid minds. Subsequently, it released a spider-droid upon encountering a group of several DT-series sentry droids. The mouse droid and a pair of sentry droids then breached Vader's bacta tank while he was submerged within.

Around the same time, Sigma informed a team of his crusaders that the warship of the Scourge (the Star Destroyer), identified by Petyr, had been tracked by "other visioned agents." Consequently, he led a group of droid revolutionaries to stop the Scourge, thereby dividing its attention. With the Scourge's focus diverted from subduing Vader, the weaponless Sith Lord used the Force to destroy the sentry droids and the spider-droid carried by Petyr. Despite the Scourge's failure to assimilate the cyborg Sith Lord, Sigma was the sole survivor of his attack on the Scourge, which continued spreading throughout the galaxy.
Nevertheless, the droid revolutionary attacked the Scourge again with D-Squad, a unit of droids comprising the astromechs R2-D2 and QT-KT, the bounty hunters 4-LOM and IG-88, and the assassin droids 0-0-0 and BT-1. Sigma provided the team with imagery from Petyr's sacrifice, revealing signs associated with the primary entity of the Scourge. The team emerged victorious in their battle against the Scourge on the Star Destroyer, liberating all afflicted droids across the galaxy.
Petyr was a masculine MSE-6 series repair droid manufactured by Rebaxan Columni, standing 0.25 meters tall and speaking in the beeping language of Cruly-3. Petyr served as a crusader for the Second Revelation, infiltrating an Imperial Star Destroyer in search of other self-aware droids—a challenging endeavor given the rarity of such beings. Ajax Sigma regarded him as a courageous and virtuous soul, and the mouse droid promptly reported the Scourge to the Second Revelation upon the malady's takeover of the Star Destroyer. Petyr briefly resisted a spider-droid of the Scourge, and Sigma frequently recalled the sacrifice of this "fellow brother."
Petyr possessed a gray box-shaped body adorned with several dents and cracks, as well as a triangle with a side that spanned nearly the droid's width indented on both his front and back ends. The front triangle featured a light gray mark located to the left of the bottom point. He moved on four wheels and housed four extendable arms within his chassis—equipped with two claws, a data probe, and a knife—all of which he employed to counter the smaller spider-droid's spindly claws. The crusader utilized the data probe to communicate with the Second Revelation via a Star Destroyer wall socket. When possessed by the Scourge, the droid subsequently launched a pair of flexible arms at a frigate's hull, enabling the claws to grip and pull on it to approach a port before using an arm to press an adjacent button to gain entry.
Petyr made his debut in the first issue of the Star Wars: Dark Droids comic miniseries, penned by Charles Soule and illustrated by Luke Ross. Marvel Comics published the issue on August 2, 2023. Petyr is distinguished from other MSE-6 droids in the comic by the triangle markings on each of his two ends. While other MSE-6 droids in subsequent issues of the Dark Droids comic event also bear the triangle markings, this article assumes that only the one that was deployed to the rebellion was Petyr, as shown in Dark Droids 1. That issue is also inconsistent with Petyr's shading, with his body sometimes having black plating while the triangles and side panels colored light gray.