Rulf Yage, a staunch Human male Moff, distinguished himself as a Grand Admiral during the Fel Empire's era in 130 ABY. Initially a member of the Imperial Navy, Yage's early career saw him leading Skull Squadron, an elite group of Predator-class starfighters tasked with safeguarding the Imperial capital world of Bastion. He later transitioned to coordinating starfighter tactics aboard the Star Destroyer Ephin Sarreti, which was part of the Second Outer Rim Fleet. Progressing in his career, Yage gained a seat on the Council of Moffs, advocating for the Navy's interests. He was once married to fellow Moff Nyna Calixte. Their marriage produced a daughter, Gunn, whom Rulf raised as if she were the son he had always desired, before Calixte left him for High Moff Morlish Veed.
As the Galactic Alliance neared its end, the Moff Council secretly aligned with Darth Krayt, the Dark Lord of the Sith, and his One Sith Order, without the knowledge of the reigning Emperor Roan Fel. Leveraging the Treaty of Anaxes, and with the Sith's support, the Moff Council declared war on the Alliance. This conflict culminated in a decisive Imperial victory above Caamas, a Core World, leading to the Alliance's surrender to Grand Admiral Morlish Veed. The Sith then assigned Yage the mission of leading an Imperial attack against the Jedi Academy on Ossus. In recognition of his role in this victory, Yage received the title "Hero of Ossus" and was appointed as a Moff. Upon his return to Coruscant, the Empire's new capital, he witnessed Darth Krayt usurp power, assassinating a decoy of Roan Fel. Krayt forced the Moff Council into submission, a demand to which Yage and the other members complied. During the pursuit of Cade Skywalker, a Jedi-turned-bounty hunter, in 137 ABY, Yage and his fellow Moffs conspired to use Skywalker to eliminate Emperor Krayt. However, the Sith had already captured Skywalker and were holding him within their temple on Coruscant. Skywalker eventually escaped and fled Coruscant aboard his ship, the Mynock, after Yage was compelled to recall the pursuing Skull Squadron to avoid violating the Sith's airspace around the temple.
Later, at a Moff Council meeting, Regent Veed tasked Yage with leading Sith-Imperial forces in Operation: Thunderstroke, an operation designed to disrupt a meeting between Fel's Empire and the New Jedi Order and to capture the exiled Emperor. Yage took command of the First Sith Imperial Strikeforce, leading the assault from the Star Destroyer War Hammer. Although Emperor Fel escaped, his daughter, Marasiah, was captured. Yage brought her to Coruscant as a prisoner before being ordered to lead the Strikeforce against those suspected of sheltering Mon Calamari refugees on the Da Soochan moon of Napdu. Yage subsequently participated in the Sith-Imperial assault against the Jedi Order's Hidden Temple, where he and his daughter led a significant number of Sith-Imperials in switching their allegiance to the Empire-in-exile. As an admiral, Yage commanded ships of Fel's Empire during the allied attack on Coruscant, which became the decisive engagement of the Imperial civil war.
Born into the distinguished Yage family, Rulf Yage was a Human male. He began his military service in the Fel Empire's Imperial Navy after graduating from the Imperial Academy, starting as a starfighter pilot. Yage joined Skull Squadron, an elite squadron flying Predator-class starfighters responsible for defending the Imperial capital of Bastion, and quickly advanced to the role of squadron commander. He married Nyna Calixte, who would later become the Director of Imperial Intelligence, and they had a daughter named Gunn, whom Rulf raised as the son he had always desired. After his time with Skull Squadron, Yage was reassigned to the Star Destroyer Ephin Sarreti, a component of the Imperial Second Outer Rim Fleet, where he managed the fleet's starfighter tactics. Yage was eventually promoted to the rank of admiral. Around this time, Calixte left him for High Moff Morlish Veed, who was also in the Navy. Yage immersed himself in his work to cope with the growing resentment in his life. Being a staunch Imperial, Yage was among those who opposed Emperor Roan Fel's announcement that his daughter, Princess Marasiah Fel, would be his successor.

When the Galactic Alliance's Ossus Project, an initiative by the Shaper caste of the Yuuzhan Vong aimed at restoring life to planets devastated during their invasion of the galaxy between 25 ABY and 29 ABY, began to negatively affect the inhabitants of these worlds, the Council of Moffs decided to invoke the Treaty of Anaxes and declare war on the Alliance in 127 ABY. A year later, the Moffs, unbeknownst to Emperor Fel, formed an alliance with Darth Krayt, the Dark Lord of the Sith Order—the same Sith group that had sabotaged the Ossus Project. By 130 ABY, the Sith–Imperial War reached its climax when Grand Admiral Veed's forces achieved a decisive Imperial victory above Caamas, a Core World, compelling the Alliance commanders to surrender. Around the same time, Coruscant fell to the Empire. The members of the Alliance's governing Triumvirate were reduced to puppets, ensuring a smooth transition from the Galactic Alliance to the Galactic Empire. Emperor Fel then appointed them as viceroys over the remaining Alliance Space.
However, the war's final act was yet to unfold. Yage, now a Grand Admiral, along with Darth Nihl, a Sith Lord, spearheaded an attack on the Jedi Academy on Ossus. Stormtroopers and Sith forces systematically eliminated most of the Jedi present, including Kol Skywalker, a Jedi Master and member of the High Council who championed the Ossus Project. For his role in the massacre, Yage, hailed as the "Hero of Ossus," was made a Moff and given a seat on the Moff Council, where he represented the Imperial Navy's interests. Following the massacre, the Council convened on Coruscant. As Moff Veed concluded his report to the Council and Emperor Fel regarding the events on Ossus, Darth Krayt and three of his followers—Wyyrlok, Maladi, and Nihl—entered Fel's throne room and proceeded to seize control of the Empire. The Dark Lord slayed the four Imperial Knight bodyguards before assassinating the individual on the throne. Although Krayt had only killed a decoy, the Moffs quickly pledged their allegiance to Krayt, their new Emperor.

Seven years into his reign, Krayt realized his body was failing. He learned about Cade Skywalker's healing power through Moff Konrad Rus's contacts on Bastion, where Skywalker had returned Princess Marasiah Fel after she was injured during a [skirmish_on_vendaxa] with the Sith on Vendaxa. The Dark Lord hoped to capture the former Jedi, convert him to the dark side of the Force, and use his abilities to prolong his own life. Skywalker arrived on Coruscant aboard his Helot-class transport, the Mynock, and was pursued by Skull Squadron, commanded by Moff Yage's daughter, Gunn "Gunner" Yage. Under orders to capture Skywalker alive, Gunn and her pilots lost the Mynock when Skywalker hid it in the Coruscant Undercity.
Rulf awaited his daughter in the Skull Squadron Hangar when Gunn and her squad mates Jae Akura, Brodie Coburn, and Tev Rimon returned. He immediately scolded his daughter, stating that losing the Mynock was unacceptable. Gunn replied that they couldn't confirm the ship's identification and that their failure was inevitable, as they couldn't risk killing Skywalker, disobeying Rulf's orders. The Moff berated his daughter, stating he didn't want excuses. Gunn suggested he dismiss her if dissatisfied. Instead, he ordered her to dinner the following evening. Akura was surprised Gunn survived her childhood, but defended her father, noting he wanted a son.
Skywalker was captured by Hands Talon and Nihl after infiltrating the Temple of the Sith to free Hosk Trey'lis, a Bothan Jedi. At a Moff Council meeting the next day, Darth Maladi announced the search for Skywalker was called off, but refused to elaborate, despite Moff Calixte's assumption he was captured. As discussions continued, Yage accused the Chiss Ascendancy of harboring Emperor Fel and his forces, speaking to Fehlaaur, the Chiss Moff. Fehlaaur and Yage argued about the Mynock sighting in the Undercity until Geist, the Imperial Army Moff, intervened, stating Skywalker was irrelevant. Geist realized the Council had less power than under Fel, and Yage blamed Calixte's machinations with the Sith. Calixte defended her actions, stating the war was going poorly. Fehlaaur and Geist offered opinions, but Morlish Veed halted the debate and called for unity before revealing his plan to capture Skywalker for the Council's purposes against Krayt's Order. Geist and Fehlaaur departed, and Yage left for dinner with his daughter, leaving Veed and Calixte to discuss their plans.

Yage met his daughter at the Naboo Queen restaurant, formerly the senatorial apartment of Padmé Amidala, a senator and one-time queen of Naboo, during the Old Republic's final days. They discussed Skull Squadron's loyalty before Moff Calixte, Rulf's former wife and Gunn's mother, interrupted. Calixte questioned her daughter about Skull Squadron's chase of the Mynock, but the meeting devolved into arguing. Rulf calmly ate his soup as Calixte and Gunn debated, interjecting when necessary, reminding his daughter that Calixte was still a superior officer. As Calixte departed, she commented on how nice their civil discussions could be; Rulf replied that they were more like civil wars, amusing his daughter.
As Skywalker's imprisonment continued, he convinced the Sith he would join them. However, in Darth Krayt's throne room in the Temple of the Sith on Coruscant, he dueled and defeated Darth Nihl, the Nagai Sith Lord who killed his father. Krayt urged Skywalker to kill Nihl, but Skywalker refused and attacked Krayt. Around the Temple, the Mynock, crewed by Skywalker's allies Deliah Blue and Jariah Syn, the Wookiee Chak, and the Devaronian Kee from the smuggling ship Grinning Liar, engaged Skull Squadron to rescue Skywalker. As Gunn locked onto the Mynock, an Imperial admiral ordered Moff Yage to recall the squadron, complying with orders that no Imperial vessels violate the Temple's airspace. Yage reluctantly complied, ordering Captain Skolitz to recall the Skulls. Skywalker and his allies fled Coruscant on the order of Cade's mother, Morrigan Corde, an Imperial Intelligence alias of Moff Calixte.
Following Skywalker's escape, Regent Veed learned of a planned meeting between the New Jedi Order and the Empire-in-exile, led by Emperor Fel, on Agamar, an Outer Rim world. Veed revealed this at a Moff Council meeting. Determined to disrupt the meeting and end the Imperial civil war, he launched Operation: Thunderstroke, aiming to capture Fel for trial and execution. The regent assigned Yage as commander of the Sith-Imperial forces.

With fellow Moff Fehlaaur as his lieutenant commander, Yage commanded the Star Destroyer War Hammer, flagship of his First Sith Imperial Strikeforce. En route to its destination in hyperspace, Yage briefed Sith pilots for the upcoming assault, informing them that Fel was located and must be captured alive. He tasked Sith pilots with flying their Fury-class starfighters as the first wave, leading Predator fighters to cripple Fel's ships and trap him on Agamar. Yage instructed them to leave no one alive except Fel and his daughter, stressing their success was compulsory. After they left, Yage told Fehlaaur that he felt he had gone from serving the Empire to leading monsters.
Yage was later in the War Hammer's hangar, speaking to Sith pilot Darth Rauder, commander of Skull Squadron for the Agamar campaign. Gunn arrived to ask her father about Morrigan Corde, who she heard was her mother, Moff Calixte. Gunn noticed Skull Squadron's Predator fighters were replaced by a new design. Moff Yage introduced Rauder and explained the Predators were replaced on Rauder's command. Gunn and the Sith argued briefly, but Gunn backed down when Rauder threatened to execute anyone questioning her orders. The Sith left, and Moff Yage questioned his daughter about making his life difficult. Gunn asked for his consul on her dilemma, careful not to reveal names or details. She said that while she wanted to act on her information, it could damage others. The Moff deduced she was referring to Corde and suggested she use her training to solve the problem, noting that killing shots were efficient but irreversible, something he learned on Ossus. Yage changed the subject, announcing they would reach Agamar soon and Gunn should familiarize her squad with their new fighters.
As delegates from the Empire-in-exile and the New Jedi Order met on Agamar, the First Sith Imperial Strikeforce emerged from hyperspace into the system and deployed its fighter squadrons. The Fel Imperial Star Destroyer Dauntless, commanded by Admiral Tohri Challon, engaged the Sith Imperial destroyers, while the squadrons engaged each other. The War Hammer destroyed the Dauntless, but Fel escaped in his shuttle. Princess Marasiah Fel was captured by the Sith Imperial forces. Acting on Veed's orders, Moff Yage brought the Princess to Coruscant one week after the battle.
When their shuttle landed, Yage escorted the Princess off. She tried to convince him to release her and defect, citing his service to Emperor Fel and his dissatisfaction with the Sith. Yage refused, knowing it would harm his daughter. The Princess said she misjudged him, stating he lacked courage and honor. The Inquisitor Darth Havok approached, demanding Yage hand Fel over for transport to Korriban per Darth Wyyrlok's orders. Yage refused, citing his instructions, but even the arrival of Regent Veed and Moff Calixte didn't convince Havok. The Inquisitor escorted the Princess away, leaving the three Moffs to argue.

Moff Veed was perplexed as to how Yage could have failed in his assigned task, but Yage defended his actions, stating that a betrayal had occurred and that they had at least managed to capture Princess Fel. He expressed his strong aversion to the Sith and their governing principles, particularly their manipulation of the Empire's personnel into mere pawns. Veed cautioned him about treason, to which Yage responded sharply, asserting that they would not hesitate to eliminate the Regent if necessary. Addressing Calixte, Yage mentioned that he would inform Gunn of Calixte's inquiries about her, noting that Gunn had only ever received such "polite falsehoods" from them. With their discussion concluded, Yage departed to prepare the Strikeforce for immediate deployment to the Da Soochan moon Napdu. However, on this particular assignment, his superiors would be the Sith Lord Darth Azard and the scientist Vul Isen, the individual responsible for the destruction of all life on Dac.
Some days later, the vessel War Hammer made its way to the Cyax system, establishing a position in orbit above Napdu. Azard and Isen made contact with the Hutt Azzim Anjiliac Atirue, who was suspected of harboring Mon Calamari refugees from Dac. When the Hutt refused to cooperate, Azard instructed Yage to deploy the bomber group Quad Victor to release the toxin that had obliterated Dac onto Da Soocha, followed by the orbital bombardment of the moon Napdu and the deployment of fighters to destroy any vessels attempting to escape the Imperial assault. The Moff was taken aback by Azard's directives, deeming it excessive, but Yage complied regardless. Once the bombers had completed their task, Yage commanded the War Hammer's turbolasers to commence firing on the moon, while Skull Squadron intercepted and eliminated any and all craft fleeing the devastation. With the operation finalized, Isen instructed Yage to order a recall before congratulating the Moff on his achievement. The scientist hailed Yage as the "Conqueror of Da Soocha" as the Moff contemplated the victory.
In the year 138 ABY, after Darth Krayt's return to power following his supposed demise, Yage and the War Hammer took part in the Sith-Imperial recapture of the planet Borosk. Following the battle, Yage received a communication from Grand Moff Veed, who believed that he had successfully eliminated Moff Calixte, Fel's informant within the Sith-Imperial ranks. In his transmission, Veed recounted his encounter with Calixte, and the Grand Moff questioned whether Yage had been aware of his former wife's true allegiance. Yage simply responded that Veed, as Calixte's lover, had also been unaware of her deception. Dissatisfied with Yage's answer, Veed threatened the Moff with severe repercussions if he could prove that Yage had possessed knowledge of Calixte's activities. After the transmission concluded, Yage revealed to his daughter that he was deeply affected by the news, however inaccurate, of his ex-wife's death, despite the absence of affection they had shared following their divorce.
Based on intelligence acquired from the interrogation of Imperial Knight Antares Draco, the Sith-Imperial forces launched an strike against the Hidden Temple, a clandestine Jedi sanctuary situated on the planet Taivas. Krayt placed Moff Yage in command of the Imperial fleet, although overall command of the operation was assigned to Grand Admiral Veed. During the initial stages of the battle, Yage's forces initiated an orbital bombardment of Taivas, but magnetic interference from the planet disrupted the Imperials' targeting systems, resulting in friendly-fire incidents and no damage to the Hidden Temple. Resorting to a ground assault led by Moff Geist, the Sith-Imperials engaged the Jedi defenders of the Hidden Temple. However, amidst the attack, the combined fleets of the Galactic Alliance and the Empire-in-exile emerged from hyperspace, effectively trapping the Sith-Imperial fleet between them and the planet.

Krayt had foreseen such a tactic and responded by deploying his contingent of Sith troopers. The arriving Sith reinforcements indiscriminately attacked both allied and Sith-Imperial forces, inflicting heavy casualties on both sides of the conflict. The troopers' disregard for their own allies prompted both Moff and Captain Yage to reevaluate their allegiances. Gunn seized the opportunity to eliminate Darth Rauder during a dogfight, announcing her decision to defect to Fel's forces to her father aboard the War Hammer. As his Sith overseer ordered the fleet to shoot down the captain, Moff Yage drew a blaster pistol and fatally shot the Sith.
Inspired by his daughter's choice, Yage transmitted a holomessage to both the Sith-Imperial and allied fleets, declaring that he and the crew of the War Hammer were pledging their allegiance to Fel, the rightful emperor. He urged other officers of the Sith Empire to follow his example or face destruction; many ships responded to the Moff's call. Imperial Knight Treis Sinde, having heard Yage's announcement, instructed a subordinate to contact the Moff to formally welcome him to the Empire-in-exile. However, with the onslaught of the Sith troopers, any hope of defending the Hidden Temple was lost, and the Alliance, Jedi, and Empire-in-exile forces were compelled to retreat with their new allies to Bastion.
At Bastion, the factions of Fel's alliance gathered for a decisive attack on Coruscant, hoping that such a move would take Krayt's Empire by surprise and shift the momentum of the war in the allies' favor. Yage, as admiral, served as one of the fleet commanders responsible for the assault on the capital, although overall command was entrusted to the senior Jedi. As preparations for the engagement continued, Yage and his daughter were joined by Morrigan Corde. Having abandoned her alias of Nyna Calixte, Corde revealed the details of her past to her former husband, including her connections to the Skywalker family, before stating that she was not seeking the Moff's forgiveness. Yage suggested that they discuss the revelation in detail at another time, but he did express his relief at seeing his ex-wife alive after Veed's attempt on her life. Shortly thereafter, Corde and the crew of the Mynock departed for Coruscant, leading a strike team to disable the capital's orbital defenses in preparation for the attack.
While the fleet made its final preparations, Admiral Yage emphasized coordination against the Sith troopers and their Annihilator starfighters during a conference with Admiral Stazi and Emperor Fel. The commanders concurred with Yage's decision to utilize the allies' combined fighter squadrons against the Annihilators and Coruscant's operational ground defenses. With the battle plan finalized, the fleet jumped into the Coruscant system just as Corde's strike force succeeded in its objective. Aided by Jedi-produced battle meditation, the armada engaged the Sith-Imperial fleet, with Yage directing Skull and Rogue Squadrons to eliminate gun emplacements on the planet's surface. As the orbital battle intensified, Corde infiltrated the Imperial headquarters and assassinated Veed; Skywalker, meanwhile, set out to assassinate Krayt.
The allied fleet sustained heavy losses, pushing its commanders to their limits. Yage attempted to contact Emperor Fel on the Imperial flagship amidst the engagement, but the Emperor did not respond, as he was preoccupied with thoughts of deploying the bioweapon Omega Red onto the capital. Fel's obsession with killing Krayt and the Sith drove him to the dark side of the Force; Imperial Knight Antares Draco was compelled to intervene, killing the Emperor and saving the lives of the allied forces who would have perished had Fel deployed the bioweapon. Skywalker, meanwhile, killed Krayt once and for all, effectively ending the war as the remaining Sith went into hiding. In the battle's aftermath, a funeral service, which Yage attended, was held for Fel on liberated Coruscant. It was at this funeral that the galaxy was formally reorganized under the authority of the new Galactic Federation Triumvirate.
Moff Yage, a devoted Imperial, hailed from a distinguished lineage. Yage possessed less cunning and deviousness compared to his peers on the Moff Council, a fact frequently pointed out by his former spouse, Nyna Calixte. She attributed Morlish Veed's position as High Moff, rather than her former husband's, to these very traits. Following his divorce from Calixte, Yage led a life filled with bitterness, which he attempted to conceal by immersing himself in his duties within the Navy. He demonstrated proficiency as a starfighter pilot and tactician, evident in his command of the elite Skull Squadron and his coordination of fighter tactics for the Second Outer Rim Fleet. His exceptional abilities ultimately earned him the rank of Grand Admiral and, following his successful assault on the Jedi Temple on Ossus, a seat on the Council of Moffs. He was known to be among the more inflexible Moffs, dissenting from Emperor Fel's decision to designate his daughter, Princess Marasiah Fel, as his successor as ruler of the Empire. Furthermore, the Moff expected unwavering adherence to his directives and had no tolerance for excuses when those under his command failed to comply. In his view, only weak individuals incapable of following instructions would attempt to justify their shortcomings.
When Gunn Yage and Cade Skywalker found themselves stranded on Tatooine, Gunn casually remarked to Skywalker about her father overlooking a few Jedi on Ossus. Skywalker expressed shock upon learning that Gunn was the daughter of the "Butcher of Ossus," but Gunn quickly defended her father's—and the Empire's—actions. She asserted that the Moff had never considered himself the "Hero of Ossus;" he had merely been following the Sith's orders. According to her, after the massacre concluded and Krayt seized control of the Imperial government, Rulf remained intoxicated for an entire week. Gunn observed that he was never the same as he was before the attack, becoming increasingly reclusive. The Moff later confided in his daughter that while delivering a fatal blow was an efficient means of dealing with someone, such an action could never be undone—a lesson he had learned on Ossus.
By the time of Operation: Thunderstroke, Yage was growing increasingly disenchanted with the Empire; he regarded the Sith under his command as nothing more than monsters, expressing his fears of becoming a Sith minion to Moffs Veed and Calixte, the former cautioning Yage about the treasonous nature of such thoughts. Yage contemplated defecting to Fel's Empire-in-exile but refrained from doing so due to his concerns about the potential consequences for his daughter. Disgusted by the Sith's lack of honor, Yage and his daughter ultimately resolved to defect during the attack on Taivas, leading numerous disillusioned Sith-Imperials in reaffirming their allegiance to Emperor Fel and later participating in Fel's assault on the Sith-Imperial capital of Coruscant.
In addition to speaking Basic, Yage possessed fluency in Durese, the language of the Duros.

Moff Rulf Yage received his initial mention in 2006's Star Wars: Legacy (2006) 0, the introductory issue of the Star Wars: Legacy series of comics. Yage would subsequently appear as a background character in Legacy (2006) 1 and Legacy (2006) 8. He would not be granted any dialogue until the Claws of the Dragon story arc; specifically, parts one, two, and six. Furthermore, he made an appearance in Star Wars: Legacy (2006) 0½, an expanded rendition of Legacy 0. In all his appearances, with the exception of Legacy 8: Allies, Yage was illustrated by artist Jan Duursema. In Allies, Adam DeKraker assumed the responsibility of drawing Yage and the other Moffs.
In Legacy 19: Claws of the Dragon, Part 6, several panels depict Yage engaging in conversation with a holographic admiral. In the first of these panels, their text bubbles are inadvertently switched—consequently, Yage is depicted uttering the admiral's line, and vice-versa. This error was not replicated in subsequent panels showcasing the remainder of their conversation. The error was later rectified in the Claws of the Dragon trade paperback. In Legacy (2006) 37, Legacy—War 1, Legacy—War 2, and Legacy—War 4, Yage is referred to as "Ranulf." When questioned about the discrepancy, John Ostrander clarified that "Ranulf" was an error, although "Rulf" could potentially be a shortened form of "Ranulf."