As part of the Galactic Empire's pacification operations in a sector of the Mid Rim Territories around 2 BBY, Imperial forces under the command of Moff Ahr carried out an attack against the insurgents based on a moon in the sector, Phelzepham. Among the governor's forces was the Sith Lord Darth Vader, who had been ordered to follow Ahr's orders to the letter by Galactic Emperor Sheev Palpatine to teach him a lesson. As Vader and the stormtrooper detachment he led pushed their numerical advantage and were on the verge of victory, Ahr decided to test his hold over Vader by ordering the stormtroopers to withdraw. Although he was suddenly left alone, Vader completed the mission and defeated the insurgents.
During the Imperial Era, the Sith Lord Darth Vader developed a reputation as being the fist of his Sith Master, Galactic Emperor Sheev Palpatine. However, when the Galactic Empire launched an attack on the astronomical object of Namzor in the Mid Rim Territories around 2 BBY, Vader disobeyed a direct order from Moff Ahr to cease his assault, resulting in both the deaths of the insurgents he had been targeting and the destruction of the coaxium stores the Empire was after. As Ahr was the political official in charge of the overall sector he and Vader were charged with pacifying, Palpatine agreed that his apprentice should not have destroyed the insurgent fortification. As such, Palpatine ordered his apprentice to obey the governor's every order to the letter until he had learned a valuable lesson.
The politician quickly began to test his hold over Vader by throwing him into missions that could have resulted in the Sith Lord being killed in action. The first instance came when Ahr's Venator-class Star Destroyer arrived at another astronomical object in his sector, Ahn Krantarium. Once there, the governor deployed a force of stormtroopers to the surface, only for the fearsome droids that had long since overrun the terrain to wipe out the entire patrol. Informed that attacking the droids would be a suicidal endeavor, Ahr ordered that Vader be sent alone. The Sith Lord ultimately triumphed over the droids and, per his master's orders, continued to show absolute loyalty towards the governor. Afterward, Ahr, Vader, and their forces traveled to the moon of Phelzepham.
Darth Vader leads Imperial stormtroopers from the front against the Phelzepham insurgents.
Another astronomical object in Ahr's sector, Phelzepham had become home to another group of anti-Imperial insurgents. As part of the pacification operations in the sector, Vader and a force of stormtroopers were dispatched onto the moon's surface from the governor's Venator to engage the group, who had set up at least one anti-infantry turret in a rocky area. The attack went well for the Imperial Military; its forces outnumbered those of the insurgents, and Vader, using the Force and his lightsaber, led the stormtroopers from the front. As many of the insurgents took cover behind the terrain of the rocky area, Vader and his soldiers fought on. At least one insurgent and two stormtroopers fell in combat, and the Sith Lord pushed back two other insurgents with a telekinesis as both factions exchanged fire.
Aboard the Star Destroyer, meanwhile, Ahr was informed by an Imperial officer the moon would likely fall to the Empire within the hour. However, instead of maintaining his numerical advantage, the politician sought to test Vader again and thus ordered all stormtroopers to fall back, leaving the Sith Lord to handle the insurgents on his own. Standing alone, Vader continued the attack despite being suddenly outnumbered and outgunned. Nevertheless, Vader triumphed in the end, although his armor was left aflame. Ignoring that, Vader returned to the bridge of Ahr's destroyer, where the governor accepted the knowledge of the Sith Lord's survival and victory as good news, only to look for another test that was likely to result in the death of the Emperor's Fist.
Ultimately, Ahr ordered for his Star Destroyer to travel into the Kankalo Belt Containment Zone and ordered for Vader, flying out of the Venator in his personal starship, to destroy the biggest threat he found within the asteroid field. Following the governor's order to the letter once again, Vader turned back to the Venator upon finding a crustaceous creature; as Vader reasoned that it was the governor who had become the biggest threat to him, he returned to the bridge and watched as the creature ripped through the viewport, taking the governor out into the vaccuum of realspace. Ahr and several other Imperials who were standing close by were killed. Palpatine sensed the murder and judged Vader, who stood tall on the bridge as stormtroopers and Imperial officers bowed to him, to have learned his lesson.
The attack on Phelzepham appeared in Marvel Comics' one-shot comic issue Age of Rebellion - Darth Vader 1 of the Star Wars: Age of Rebellion series. Written by Greg Pak and illustrated by Ramón Bachs, the comic was released on June 26, 2019.