Vaylin was a Human female who possessed sensitivity to the Force, daughter to Valkorion and Senya Tirall. She was the younger sister of Arcann and Thexan, twin brothers. From a young age, Vaylin showcased immense Force potential, yet controlling her proved challenging. This led Valkorion to confine her on Nathema, fearing she might one day pose a threat. Within Nathema's Sanitarium, Vaylin endured brutal mental and physical torment, shattering her innocence and transforming her into a ruthless individual devoid of empathy. Senya's attempt to rescue her daughter was thwarted by Valkorion, leading Vaylin to resent her mother for her suffering. Subjected to a unique mental conditioning known only to Valkorion, Vaylin was eventually permitted to return to Zakuul, where she patiently awaited her opportunity instead of immediately retaliating. Following Valkorion's assassination orchestrated by Arcann, who blamed the Outlander, Vaylin sided with her brother and assumed the role of High Justice under the new Emperor. Together, they swiftly conquered both the Galactic Republic and the Sith Empire in under a year.
After five years of Arcann's rule, Lana Beniko freed the Outlander from carbonite imprisonment. Vaylin spearheaded the pursuit but failed to prevent their escape. The fugitives, aided by Senya, eventually fled on the Gravestone, further fueling Vaylin's hatred towards her mother, who now opposed her own children. Vaylin confronted Senya in battle and revealed Arcann's role in Thexan's death. Vaylin led a series of reprisal bombardments personally, aiming to draw the Outlander out of hiding. She also inspected the Gilded Star when Senya, disguised as Vaylin, assisted the Outlander in raiding the treasury ship. During the Battle of Odessen, Vaylin betrayed Arcann, revealing his location to the Alliance while simultaneously luring Senya away for a personal confrontation. However, Arcann intervened, preventing Vaylin from striking a blow, after which Senya took him away. Vaylin returned to Zakuul to discover that SCORPIO had seized the Eternal Throne in their absence. Surprisingly, the droid offered the Throne to Vaylin, offering to serve as her advisor.
As the newly appointed Eternal Empress, Vaylin launched a manhunt for Arcann and Senya, encountering her mother on Ord Mantell, where she mercilessly slaughtered numerous Knights of Zakuul loyal to Senya. Tracking them to Voss, Vaylin initiated an invasion to force her family out of hiding. However, she was unable to eliminate them due to the newfound self-preservation instincts of GEMINI droids, granted by SCORPIO. Capitalizing on rumors of the Outlander's demise, Vaylin and SCORPIO launched an assault on the Gravestone, seizing control of the only vessel capable of challenging the Eternal Fleet. During a counter-attack by the Alliance, Vaylin nearly killed the Outlander when Valkorion, residing within the Outlander, activated her conditioning, revealing its existence to Vaylin for the first time. SCORPIO commandeered the Gravestone and the Eternal Fleet to Iokath, where Vaylin led her Zakuulan forces to reclaim the Eternal Fleet from ARIES and discover a method to restore GEMINI to their original programming. At the Grand Festival of Empress Vaylin, Vaylin was confronted by the Outlander and Arcann, who had joined forces to end her reign. Vaylin retreated to Nathema, where the Anomid scientist Jarak, responsible for her conditioning, assisted her in breaking free. Immediately after, she launched an Assault on Odessen. During the ensuing battle, the Outlander provoked Vaylin into a direct confrontation, resulting in Vaylin's death. However, Valkorion secretly absorbed her spirit's power and enslaved her, using it to overcome the Outlander's mental defenses. As the Outlander battled Valkorion for control, Valkorion deployed Vaylin's enslaved spirit against his opponent. Instead, the Outlander freed Vaylin from Valkorion's control, using Dramath's holocron. Vaylin then joined the Outlander and her family in the fight against Valkorion, leading to the final demise of the Immortal Emperor and allowing Vaylin's spirit to find peace. When Valkorion's imprint spirit resurfaced years later, attempting to resurrect himself within the mind of Jedi Grand Master Satele Shan, Vaylin's spirit joined forces with the Outlander and all those manipulated or killed by Valkorion, finally destroying the ancient entity for good.

Vaylin was born to Valkorion, the Immortal Emperor of the Eternal Empire (secretly the ancient Force entity Tenebrae), and Senya Tirall. She was the younger sister to twin brothers Thexan and Arcann. She inherited immense strength in the Force from her father, who was over a millennium old. Even before her birth, Vaylin's power was evident, causing furniture to move while she was still in her mother's womb. As a toddler, Vaylin dismantled droids and once crippled a guard who dropped a ball she threw. The children would play together, sparring near the Eternal Fleet or running away to live in the Endless Swamp for a month. Her mother loved her, spending much time with Vaylin, playing in the fields and forests of Zakuul. Senya tried to teach Vaylin to rely less on the Force and more on her own abilities, once stopping her from levitating a wooden toy.

Vaylin observed her older brothers training in combat against the Knights of Zakuul and, wanting to emulate them, attempted the same techniques on an old, rusty suit of Knight armor while alone in the woods. Frustrated by her inability to land simple Force attacks on her training dummy, Vaylin became enraged, destroying the entire suit. Once she was old enough to begin her own combat training, Vaylin grew frustrated with having to use wooden sparring sticks instead of her Force abilities. During one exercise, she became frustrated at her defeats and unleashed her powers, levitating several Knights simultaneously before crushing them in their own armor, an incident witnessed by her father. As Vaylin matured, the Immortal Emperor noticed similarities between them, which both pleased and frightened him, leading him to keep a close watch on his favored child.

Fearing a future challenge, Valkorion sought to limit and control Vaylin's power. He took her to Nathema, his birthplace from centuries prior, now a lifeless world devoid of the Force after he used the Ritual of Nathema to eradicate all life, granting himself immortality. Vaylin cast one last glance at her mother before being taken into the Sanitarium, the last standing and inhabited structure on the planet, where she was placed under the care of Anomid scientist Jarak. Jarak was tasked with subjecting Vaylin to strict mental conditioning, using any methods that did not result in her death.

Vaylin endured brutal experiments at the hands of the Nathema Zealots, who covered her arms in ritualistic tattoos and shaved her head, permanently darkening her hair. Jarak subjected Vaylin to constant fear, pain, and isolation, testing her both physically and mentally. She was forced to observe test subjects being torn apart by creatures, witness the dissection of their corpses, and experience the effects of chemicals and implants. Vaylin blamed her suffering on her mother, believing she had been abandoned, and developed an intense hatred.

Sensing her daughter's anguish, Senya resolved to rescue Vaylin from Nathema. Infiltrating the Sanitarium, she found Vaylin unconscious and carried her to the shuttle landing platform. There, six Nathema Zealots blocked their path. After Vaylin opened her eyes, Senya told her to stay back while she knocked out the Zealots. Senya asked Vaylin to come with her, but her daughter's eyes were filled with hate. Valkorion emerged from the Sanitarium and ordered Knights to restrain Senya, taking Vaylin back inside. Deciding her children were unsafe around Valkorion, Senya attempted to flee with them, but they idolized their father and refused to leave, calling their mother weak, forcing her to leave alone.

Vaylin spent years on Nathema, only visited by her brother Thexan, who brought her gifts from conquered worlds. Eventually, Jarak exhausted conventional methods and subjected Vaylin to torture by machines of his own design. Vaylin's mind was broken, and she became a cruel, vindictive person prone to temper tantrums. However, she remained unaware of the true purpose of her confinement: to be conditioned to become powerless against anyone who spoke the code phrase "Kneel before the Dragon of Zakuul" in her presence. While effective, the conditioning worsened Vaylin's violent tendencies and mental instability, turning her into a monster.

With Vaylin's power restrained, Valkorion allowed her to return to Zakuul. Arcann traveled to Nathema to bring Vaylin home. Back at the Spire, Vaylin entered the Eternal Throne room, where her father sat with her brothers. She stated that he should have left her on Nathema. Valkorion replied that his daughter belonged at his side and presented Vaylin with her first lightsaber. Vaylin ignited the blade, prompting Arcann and Thexan to defend their father, who ordered them to stand down. To their relief, Vaylin deactivated her lightsaber and knelt before Valkorion, acknowledging his superiority.

During the Cold War and Galactic War, the Immortal Emperor temporarily inhabited other bodies, using the Emperor's Voices to manipulate his Sith Empire in a war against the Galactic Republic. However, his focus remained on Zakuul. When his Voice was killed during a Dromund Kaas operation, the Emperor was weakened, and his spirit was trapped on Yavin 4, unable to regain his full strength or return to his physical form for over a year. During this time, Vaylin discovered that, without her father suppressing her, she could access the full extent of her powers.

Vaylin developed a close relationship with her brother Arcann, as he shared her disdain for destiny. She bided her time, studying her prey like a predator. Valkorion eventually returned to Zakuul, but Vaylin did not openly rebel. Soon after, Arcann and Thexan led a series of Eternal Empire raids into the Core Worlds to test their strength. Arcann was injured, losing his left arm and receiving cybernetic replacements, as well as wearing a mask over the scarred half of his face. Upon returning, Arcann was provoked by Valkorion's indifference and attacked his father, accidentally striking Thexan instead.

Arcann later brought two survivors from an initial skirmish with the Eternal Fleet, Darth Marr and the Outlander, to their father's throne room. The prisoners identified Valkorion as Vitiate, the former Sith Emperor. When Valkorion offered them a chance to kneel, Darth Marr refused, and Valkorion struck him down with Force lightning, killing the Dark Councillor. Vaylin then ordered all Knights and Scions to leave the room, leaving Arcann and Valkorion alone with the Outlander, to whom Valkorion offered a share of his power. Arcann used this opportunity to betray his father, and Valkorion was struck down, though his spirit attached itself to the Outlander.

When Vaylin returned, Arcann blamed the Outlander for their father's death and claimed the Eternal Throne as the new Emperor of Zakuul, declaring a conquest of the Core Worlds in retaliation and freezing the Outlander in carbonite. Vaylin became her brother's High Justice, a position previously held by Yuriem, effectively becoming the second most powerful person in the Eternal Empire. Within a year, both the Sith Empire and the Galactic Republic surrendered to Zakuul, signing peace treaties. Vaylin was present when Republic Senator Evran and Sith Empire Dark Councillor Darth Vowrawn pledged their loyalty to Arcann, and after they left, she sensed an unseen presence in the room. Arcann asked what it was, but Vaylin stabbed the empty spot where she sensed the presence with her lightsaber.

In 3631 BBY, five years into Arcann's reign, Vaylin personally responded to an alert in the vault containing Arcann's most prized possessions, including the carbonite slab with the Outlander. A Knight of Zakuul reported that intruders had released the Outlander and that skytroopers were slowed by alarms. Vaylin executed the Knight and destroyed a holocamera she was being observed through. Vaylin followed the escapees' trail, easily destroying a thick door and damaging a Sun Generator near a skytrooper factory in an attempt to catch them in the blast.

Vaylin finally cornered the Outlander and their companion Lana Beniko on a landing platform, preparing to deal with them personally when a shuttle piloted by Koth Vortena arrived and opened fire. Vaylin telekinetically shielded herself with debris while her skytrooper squad was cut down. This allowed her targets to board the ship, which Vaylin damaged but couldn't prevent from escaping. She then responded to a holocall from her brother, informing him of the Outlander's escape. Vaylin returned to the Eternal Throne room, where Arcann determined that the damaged shuttle could only land in the Endless Swamp and ordered skytrooper forces to sweep the area. Vaylin executed a Knight responsible for security in the carbonite prison for failing to provide a satisfactory explanation.

The Outlander's accomplices located the Gravestone, a legendary starship that had once overpowered the Eternal Fleet, and got it airborne. The vessel faced the Eternal Fleet as it tried to escape Zakuul, and after Vaylin inquired about Arcann's hesitation, he ordered his ships to open fire. However, one omnicannon blast from the Gravestone destroyed over two dozen Eternal Fleet warships before jumping into Hyperspace, impressing Vaylin with the ship's power. After questioning and killing three Zakuulan Knights who claimed the Outlander was allied with their mother, and another three because she felt like it, Vaylin reported her findings to Arcann. Vaylin wondered if Senya knew about Valkorion's survival inside the Outlander and was trying to restore his rule, claiming that she and Arcann no longer needed their parents, who gave them power to forge their own future. Vaylin later received a tip from a Zakuulan socialite that the Outlander and her mother were spotted in Zakuulan Old World and informed Arcann, though he declined to pursue them at the time.

Heskal, the exiled leader of the Scions of Zakuul, informed Arcann that the Outlander was hiding on the Asylum shadowport, and he went there with Vaylin to deal with them personally. In the battle of Asylum, Vaylin led the Eternal Empire forces towards the Gravestone, where Arcann ordered her to spare no one and announced her intention to kill the Outlander's friends. However, her mother intervened and pushed the Outlander out of Vaylin's reach. After a brief exchange, Vaylin attacked her mother, and the two engaged in a Lightsaber duel as Senya tried to reason with Vaylin, without success. Senya disarmed Vaylin and had her at her mercy but couldn't deliver the final blow.

This amused Vaylin, who revealed that Arcann had killed Thexan in cold blood, not during the fighting in the Core Worlds. Senya retreated on the Gravestone with other dissidents, after which Vaylin found Arcann and declared she would kill their mother for sparing her life. Returning to Zakuul, Vaylin listened to her brother lamenting that Valkorion was now plotting against his own children. She mentioned that Senya would likely want his head for killing Thexan before reassuring Arcann that the Eternal Empire would keep her at bay. Arcann remarked that Thexan should be alive, ruling the Empire alongside his brother and sister as it was meant to be. Vaylin admitted she would like Thexan back but shrugged off the nostalgia and reminded Arcann that their father now favored the Outlander and planned to take everything from them.

On her brother's orders, Vaylin scouted five sectors for the Outlander and the Gravestone, without success. She returned to Zakuul to report her failure, jokingly calling their problems figments of their imagination. Arcann ordered Vaylin to bombard one inhabited world in each of the five sectors into dust, believing it would loosen some tongues. Vaylin carried out her orders, even recording holos of her handiwork, only to return and hear that the Outlander had attacked Zakuul again in her absence. Blaming the Knights of Zakuul for their inability to apprehend the Outlander, Arcann ordered them to fight to the death in pairs as punishment and motivation. Vaylin expressed concern that their hunt for the Outlander would be severely hampered with half their Knights dead, but Arcann ignored her and barked at her to proceed when she hesitated.

Interrupting her brother's meditative state, Vaylin used her telekinetic abilities to seize his lightsaber, expressing her unhappiness with his pessimistic attitude. Arcann admitted his aggravation with their father's refusal to confront him directly, leading Vaylin to suggest that Valkorion was punishing Arcann for usurping his position. Arcann countered that their father had always been devoid of emotion, even following Thexan's demise. This prompted Vaylin to fondly remember Thexan's habit of bringing her gifts from the worlds they had conquered. Arcann then reminded her that he had freed her from Valkorion's control, asking if he still had her backing, to which Vaylin confirmed her support.

Later, Vaylin journeyed to Vandin to inspect the covert treasury ship, known as the Gilded Star. Initially thinking she had arrived just in time to thwart the thieves, she was enraged to discover the ship's vault completely empty, and even more so upon learning that her mother had assisted in the robbery, disguising herself with Vaylin's appearance. Upon her return to Zakuul, she began indulging in fantasies of revenge against her mother, but Arcann interrupted her angry outburst by inquiring if she remembered Senya from their childhood. Vaylin reiterated her conviction that Senya resented and manipulated her due to her greater power, and questioned what would happen when the rest of the galaxy found out about the insult they had suffered, which would incite other worlds to rebel. Arcann then reassured her that the stolen wealth could be recovered and that the fear of his power would prevent any further insurrections.

Subsequently, Arcann and Vaylin observed a holographic report displayed in real-time, depicting a Mandalorian army attacking an Eternal Empire weapons factory located on Darvannis. Vaylin suggested deploying the Eternal Fleet to obliterate the Mandalorians, but Arcann expressed confidence in the factory's ability to defend itself. As the battle intensified, the Mandalorians gained an advantage, and Arcann, noticing their apparent inspiration by a cause, realized that the Outlander was present on Darvannis alongside them. He prepared to dispatch the Fleet to Darvannis, but Vaylin reminded him that their ships would not arrive in time and criticized her brother for disregarding her earlier advice.

While Vaylin threatened to execute a Knight of Zakuul for the loss of the Darvannis factory, Arcann received an urgent communication from an Eternal Fleet warship reporting that the Outlander and Senya were attempting to seize control. Vaylin eliminated the incompetent Knight from the platform and joined Arcann aboard his Eternal Flagship, where they gathered a substantial contingent of the Eternal Fleet and hurried to intercept their target. However, the Gravestone once again escaped into hyperspace just as the Eternal Fleet arrived. Following this, Vaylin informed her brother that all Eternal Fleet vessels outside their current sector were not responding to commands. Arcann dismissed this development as insignificant, prioritizing the pursuit of the Outlander and Valkorion over concerns about the Eternal Fleet. Unbeknownst to them, SCORPIO, an advanced artificial intelligence, had seized control of the Eternal Throne in their absence, thereby controlling both the Skytroopers and the Eternal Fleet, and consequently, their entire Empire.

In an effort to incite her enemies to destroy one another, SCORPIO disclosed her actions to Arcann and Vaylin, revealing that the Alliance base was situated on the planet Odessen. Arcann commanded his detachment of the Eternal Fleet to attack Odessen, intending to deal with SCORPIO after eliminating the Outlander and his father. As the battle of Odessen intensified, the Outlander, Senya Tirall, and Lana Beniko boarded the Eternal Flagship with the goal of assassinating Arcann. Upon spotting her mother on the security monitors, Vaylin contacted them via a loudspeaker, revealing Arcann's location on the ship's bridge while simultaneously luring Senya away from him to confront her personally.

The Outlander engaged and defeated Arcann on the bridge, crushing him beneath a pile of debris. However, Senya arrived shortly after the Outlander's departure and rescued Arcann from the rubble. Vaylin then returned to the damaged bridge, declaring that her mother was, as always, too late and accusing her of weakness for abandoning her children. Senya offered both of her children a chance to return to her, which Vaylin rejected, launching herself at her mother, only to be Force-pushed away by Arcann. Feeling betrayed by her brother, Vaylin demanded to know why he had saved Senya's life, but before she could receive an answer, falling debris forced her to retreat and flee back to Zakuul, while Senya escaped with Arcann in his shuttle.

Upon returning to Zakuul, Vaylin fought her way through SCORPIO-controlled skytroopers in the Eternal Throne room, but then sheathed her lightsaber after SCORPIO commanded her droids to cease firing. SCORPIO welcomed Vaylin, explaining that she had only seized the throne to grant free will to the Fleet's GEMINI droids. Vaylin asserted that she was more deserving of the Eternal Throne's power than Arcann and was surprised to find a kindred spirit in SCORPIO, someone with immense power and potential who felt constrained by lesser beings. Astonished that SCORPIO did not desire to control her creations, Vaylin agreed that the ability to choose made them stronger, relating to her own experiences. SCORPIO then willingly relinquished the Eternal Throne to Vaylin, offering to remain and advise the new Empress of Zakuul on how to destroy their enemies.

As the new Eternal Empress, Vaylin quickly demonstrated herself to be an even more ruthless leader than Arcann. During her coronation, she publicly executed a dozen Knights of Zakuul for failing to protect her brother, after personally congratulating each victim on the great honor of dying at her hand, an act of cruelty that horrified Zakuul's citizens. Having eliminated the entire group of Arcann's guards, Vaylin replaced them with an elite unit selected from the remaining ranks of the Knights of Zakuul, which she named the Horizon Guard. She also declared a bounty on her own mother, relentlessly pursuing every lead. Eventually, Vaylin discovered that several dissident Knights, fearing that she might disband or destroy their order, were planning to meet with Senya on Ord Mantell.

Vaylin traveled to Ord Mantell and massacred the host before Senya arrived on Arcann's shuttle. She then announced her presence by igniting spilled rhydonium with Force lightning, before snatching her mother's lightsaber pike from her grasp. Using the Force, Senya summoned a fallen Knight's lightsaber to her hand to defend herself, with Vaylin accusing her mother of being afraid, while Senya implied that her daughter was taking orders from SCORPIO. Vaylin fought fiercely against her mother, but Senya's combat experience and the empress's flawed techniques allowed Senya to hold her own. Senya once again attempted to reason with her, but Vaylin was solely focused on killing her mother and attempted to deliver a final blow, only to strike a Zakuul shuttle's damaged hyperdrive. Vaylin managed to shield herself and Senya from the resulting explosion with the Force, allowing Senya to escape. It remained unclear to Senya whether there was a part of her daughter that still cared for her or whether she was a predator toying with her prey.

Following the events on Ord Mantell, Vaylin tracked Senya and Arcann to Voss and invaded the planet with the Eternal Fleet, intending to force them out of hiding. Her forces landed in and captured the capital city of Voss-Ka, after which Vaylin gleefully ordered the planet to be burned to ashes. The fighting continued over time, with Vaylin becoming angry that the planet was being torched without her, when SCORPIO noted from a presence of Mandalorian forces in Voss-Ka that the Outlander was on-world as well, with the spirit of Valkorion inside. Vaylin located all three of her family members inside the Shrine of Healing and addressed them through a Skytrooper holocomm, taunting her family and ordering the Eternal Fleet to bombard the Shrine in an attempt to kill them all. However, before the Eternal Fleet ships could scorch the planet's surface, the Imperial fleet had arrived and caused the GEMINI units to flee the battle. Vaylin was angered at them for retreating without orders, but SCORPIO noted that the GEMINI merely made a choice she did not like and urged the Empress to focus on the big picture, bringing her attention back to the Outlander.

Shortly after the battle of Voss, news arrived from Dromund Kaas reporting the death of the Outlander. Although Vaylin could sense that this was not the case due to Valkorion's continued presence, SCORPIO pointed out that the resulting chaos presented the perfect opportunity to strike against the Alliance. Vaylin and SCORPIO devised a trap for the Gravestone by seizing a civilian cargo freighter called the Ridala, murdering its captain, and simulating an attack by the Eternal Fleet. When the Gravestone, piloted by Koth Vortena, arrived to confront the Fleet, SCORPIO impersonated the freighter's captain and sent a distress signal. Vortena allowed the shuttle to land inside the Gravestone's hangar for repairs, from where SCORPIO, Vaylin, and a contingent of Knights of Zakuul and Horizon Guard took control of the vessel.

Vortena secured the bridge and managed to evade capture, contacting the Alliance for assistance. The Alliance fleet arrived and engaged the Eternal Fleet, while the Outlander and Lana Beniko infiltrated the Gravestone via a boarding pod. The Gravestone's computers were protected by Vortena's personal key, and SCORPIO was unable to access the HoloNet signal during the battle, so Vaylin tortured Vortena's second-in-command, Len Parvek, for his personal information. SCORPIO unlocked the bridge controls, but then observed that five patrols at opposite ends of the ship had been lost, revealing that Vortena was receiving assistance from the Outlander. Vaylin proceeded to confront her father, encountering and attacking Lana Beniko at the Dark Sanctuary.

Their battle was interrupted by the arrival of the Outlander and Koth Vortena, who warned Vaylin about a quantum bomb hidden beneath the floor, which had just been triggered by the fighting. Feeling that she had waited long enough, Vaylin attacked the Outlander and was about to land a blow when Valkorion himself intervened to protect his host. He paused time in his vicinity, but Vaylin was able to break through and regain her freedom of movement, a feat previously unseen even by her father. Engaging in a conversation with her father for the first time since his death, Vaylin blamed him for confining her like an animal, while Valkorion insisted that they were family and that his actions were intended to keep her safe. Valkorion then used Vaylin's conditioning against her, rendering her powerless with the phrase "Kneel before the Dragon of Zakuul".

Realizing that there was another mental block in her mind for the first time, Vaylin became enraged and confused, fleeing the Dark Sanctuary. At this point, SCORPIO announced that she was seizing control of the Gravestone, and Vaylin returned to the bridge, determined to deal with yet another betrayal. She attempted to attack the droid, but SCORPIO was faster, and Vaylin was shot in the shoulder by SCORPIO's blaster, just as the Gravestone jumped into hyperspace. Both Vaylin and SCORPIO then departed the bridge. The Gravestone and the Eternal Fleet arrived in the Iokath system, where SCORPIO boarded the shuttle Ridala and left, while Vaylin and her remaining soldiers proceeded to sabotage everything they could on the Gravestone. Returning to the ship's bridge, Vaylin overpowered the Outlander's reinforcements, including Kaliyo Djannis and Aric Jorgan. The Outlander contacted the bridge again, and Vaylin responded, announcing her intention to kill either Torian Cadera or Vette for one of her trophy cages. However, before she could harm anyone, the ship was engulfed by the blinding light emanating from Iokath.

Vaylin awoke in a cell with metal walls and no visible exits, and began pacing angrily, using the Force to tear panels from the walls. She then heard a familiar voice and was surprised to see her deceased brother Thexan standing before her. Hearing her brother say that he missed her shocked Vaylin, who asked why he had waited so long to appear after his death at Arcann's hands. Thexan claimed that he wanted to help her, asking what prevented Vaylin from destroying the Outlander. Vaylin immediately became suspicious when she could not sense her brother through the Force and asked Thexan about the time he came to Nathema to bring her home. As soon as the conversation proceeded normally, Vaylin realized the deception, revealing to "Thexan" that it was Arcann who had brought her home.

Demanding to know the identity of the imposter, she gathered a collection of wall panels into a projectile and telekinetically hurled it at "Thexan", shattering a wall and revealing an exit. Outside on Iokath's surface, Vaylin destroyed several hostile droids before spotting "Thexan" once more. She demanded to know the impostor's identity, and the apparition revealed itself as the hologram of ARIES, Iokath's caretaker. Vaylin then encountered the remains of Zakuulan crews who had also been transported to Iokath from the ships of the Eternal Fleet, including a number of GEMINI captains. She rallied her forces to reclaim the Eternal Fleet, and when one GEMINI captain refused out of fear, she threw her over the railing.

Together, they located the control console, from which one of the GEMINI captains released the docked Eternal Fleet warships. However, as the ships prepared to depart, they began colliding with the energy shield that encircled the planet, and Vaylin ordered them to locate and disable its source. She was then sniped by a purifier droid drone, responding by telekinetically thrashing it around until the droid's limbs were destroyed, rendering it harmless. She brought the droid with her to one of the ships, where a Knight informed her that half of the Eternal Fleet had been recaptured, while the remaining ships could be towed with Tractor beams.

Vaylin ordered the GEMINI captain to connect to the Purifier drone and access its information about ARIES, which revealed that ARIES base in the southern hemisphere was about fire a weapon that would destroy organics and the GEMINI droids alike. Vaylin ordered the Eternal Fleet to bombard that fortress, to which the Purifier drone noted that the GEMINI functioned sub-optimally due to SCORPIO's free will protocols, which had brought their senses of self-preservation to the fore, to the point of questioning or outright ignoring Vaylin's orders. However, the Outlander's team then disabled the planetary shield, allowing the Eternal Fleet to escape. Vaylin insisted on killing her enemies first and ordered the Purifier drone to override the GEMINI captain's programming, restoring it to the default setting.

The superweapon detonated, threatening to engulf Iokath in radiation, prompting Vaylin to flee into hyperspace with the majority of the fleet, while leaving behind several vessels to pursue the Gravestone and its crew. Contact with the pursuit vessels was lost, and Vaylin, determined to have a fleet that obeyed her without question, brought the Purifier drone with her back to Zakuul, where she plugged it into the Eternal Throne. The purifier used the connection to reprogram every single GEMINI unit, which Vaylin tested by ordering one ship in the fleet to destroy another, which it did without hesitation. Satisfied with the result, Vaylin then smashed the Purifier into dust.

With her full control over the GEMINI captains restored, Vaylin dispatched the Eternal Fleet to hunt down and destroy Alliance patrols, outposts, and supply convoys. She also wasted no time attempting to break her mental blocks and ordered Jarak to return to Nathema and discover a method to undo the conditioning he had imposed on Vaylin, making it clear that failure would result in death. To commemorate her accomplishments, Vaylin instructed her Magistrate of Revelry, Indo Zal, to organize a Grand Gestival in her honor at the Palace of the Eternal Dragon. During the party, Vaylin planned to execute a number of captured Zakuulan rebels by feeding them to wild beasts.

Shortly before the party commenced, Vaylin experienced the apparition of Valkorion's spirit in the room, who attempted to further break her by activating her conditioning with the phrase "Kneel before the Dragon of Zakuul". Vaylin instinctively drew her lightsaber, but the only other being physically present in the room was Indo Zal, who informed her that everything was prepared for the party and that the rebels were adorned with shock collars, the controls for which were given to the Empress. Vaylin later received a holocall from Jarak, who informed her that a breakthrough had been achieved in his research efforts, and Vaylin responded that she would depart to him as soon as the rebels were dealt with. However, she then observed Indo Zal acting suspiciously and realized that he was working against her with the Alliance, fitting him with a shock collar of his own.

Ahead of schedule, Vaylin delivered her address to the assembled social elite of Zakuul, which was also broadcast across the galaxy via numerous holocameras. At this point, the Outlander and his Alliance ally, Theron Shan, revealed themselves to Vaylin, mocking her in front of the crowd and causing her to release the prisoners into the beast pit. Vaylin intended to use the Force to crush the two with heavy mental ornaments, but the Outlander triggered her conditioning, causing Vaylin to lose control of her powers in front of everyone, before detonating the Ion charges they had attached to the security relays. The ion blast disabled all electronics nearby, including the prisoners' shock collars, which freed them to attack, and the locks that secured the wild beasts, releasing them into the crowd of civilians and the Knights of Zakuul. Vaylin drew her lightsaber and prepared to confront the Outlander in combat, but at this point Arcann joined the fray with a group of his loyalists, arriving in a shuttle and launching an assault on the palace.

Upon seeing her sibling, Vaylin turned away from the main chamber of the palace, heading towards a secluded balcony and destroying every holocamera in her path. Arcann followed Vaylin to the balcony, attempting a peaceful resolution, but Vaylin, convinced of Arcann's involvement in her manipulation, launched an aggressive assault. The siblings then began an intense lightsaber combat, which was disrupted by the arrival of the Outlander and Theron Shan. Recognizing an opportunity to strand Arcann with their father's ship, Vaylin hurled a speeder bike at him, using the distraction to escape to her personal flagship. Aboard, she witnessed a galaxy-wide holographic declaration of Arcann pledging allegiance to the Outlander's Alliance. Consumed by fury, Vaylin commanded the Eternal Fleet to obliterate the Palace, even Force-choking a Horizon Guard who dared mention the supporters still inside. The Outlander and Arcann successfully fled, while Vaylin steered her flagship towards Nathema, leaving Zakuul in turmoil, divided between her loyalists and those in open revolt.

Driven by a desperate desire to overcome her mind control, Vaylin made her way back to the Nathema system. A shuttle transported her, along with a contingent of Horizon Guards, to the entrance of the Sanitarium, where they were greeted by a Keeper of the Abyssin species, who informed Vaylin that Jarak awaited her within his laboratory. Ordering the Horizon Guards to remain outside, the Empress ventured into the facility, reaching the habitat where Jarak conducted his disturbing experiments. A group of three mutated Acklays surrounded her, posing an immediate threat, leading Vaylin to realize that the void of Nathema blocked her access to the Force, forcing her to use her lightsaber to eliminate the creatures.

Jarak arrived on the scene, observing that the creatures' aggression stemmed from her fear and hatred, and informed Vaylin that preparations were complete in the main lab. There, Vaylin observed a vast circular arena, ringed by colossal energy nodes and attended by Nathema Zealots, which Jarak promised would sever her mental bonds, provided she survived. Vaylin inquired about the survival rate of Jarak's previous test subjects, and despite the Anomid's admission that none had been strong enough, she agreed to proceed. Energy beams from the pillar orbs pierced Vaylin's body, causing immense pain and triggering uncontrolled bursts of her power. As Vaylin fought against the agony, the Force energy emanating from her vaporized several Keepers and Zealots, prompting Jarak to flee for his own safety.

Now isolated and at the mercy of Jarak's contraptions, Vaylin endured excruciating pain, unleashing waves of energy that threatened to destroy the entire Asylum. Ultimately, determined to avoid dying in the place she despised, Vaylin summoned her remaining strength and overwhelmed Jarak's machines, causing them to detonate one after another, freeing her from their grip. Immediately after the pain subsided, Vaylin sensed that her mental restraints were broken and left the surface of Nathema. Returning to her flagship, a Horizon Guard asked if the Empress had found what she sought, to which Vaylin responded by using Force Crushing on everyone else on the bridge and remotely triggering the Sanitarium's destruction, before ordering her ships to depart Nathema's orbit. She then set a course for Odessen with the entire Eternal Fleet, determined to eliminate the Alliance once and for all.

Now unburdened by her conditioning, Vaylin immediately initiated an assault on Odessen, intending to destroy the Alliance and her family members who opposed her. Her attack occurred at a precarious moment for the Alliance, as the Gravestone was grounded, awaiting the installation of upgrades acquired from Iokath. Without the Gravestone, the Alliance fleet was unable to prevent Vaylin's ground forces from landing, and soon World thrashers were clearing landing zones in the Odessen wilderness, facilitating the deployment of troops and a large number of Eternal Empire Walkers from Zakuul Hovercrafts. Despite being outnumbered by Vaylin's legions, the Alliance's ground forces mounted a surprisingly strong defense.

From the bridge of her flagship, Vaylin oversaw the battle, acknowledging that while her victory was assured, the Eternal Empire would suffer significant losses, and instructed her forces to accept any cost necessary. Later, the Gravestone managed to launch and join the fleet engagement, after which Vaylin received a taunting communication from the Outlander, designed to lure her to the surface for a direct confrontation. On Odessen, Vaylin seized one of the Outlander's allies as a hostage and challenged Valkorion's vessel to face her on the Alliance base landing platform. There, Vaylin confronted Senya, Arcann, and the Outlander, supported by a contingent of skytroopers and Horizon Guards, questioning what Valkorion saw in the Outlander.

Her father then materialized before her, declaring Vaylin unworthy of the Eternal Throne and unfit to rule the Eternal Empire, prompting Vaylin to hurl her hostage at the Outlander as a sign of contempt, simultaneously using the Force to break the unfortunate fighter's neck. Vaylin then engaged her mother, brother, and the Outlander in combat, and after appearing to be defeated, unleashed her power in a massive Force Storm. With no other recourse, the Commander was compelled to strike Vaylin down, ending her life.

Following Vaylin's death, the remaining Zakuulan forces on Odessen surrendered, but with the Eternal Throne vacant, the GEMINI captains reverted to their default programming, ordering the Eternal Fleet to indiscriminately bombard the capital worlds of Coruscant, Dromund Kaas, and Zakuul. Meanwhile, Vaylin's essence persisted, as her spirit was absorbed by Valkorion into the Outlander's body, providing the Immortal Emperor with the means to overcome his vessel's mental defenses. As soon as the Outlander claimed the Eternal Throne, Valkorion betrayed them, trapping them within the depths of their own mind.

The Outlander resisted, and Valkorion summoned Vaylin's enslaved spirit, placing her under his control and commanding her to destroy the Outlander. The Outlander fought Vaylin in the mental realm and triumphed, but Valkorion easily restored her spirit, after which the Outlander used a representation of Dramath's holocron to free Vaylin from her father's mind control. At this moment, Arcann joined them within the Outlander's mind, using the physical holocron located in the Eternal Throne room. The Outlander and Arcann persuaded Vaylin to join them against Valkorion, who had enslaved her in the past and would do so again, and the three of them attacked the Immortal Emperor.

After toying with them for a time, Valkorion shattered the Outlander's holocron, asserting that nothing could stop him. However, because his spirit was now linked to Vaylin's and shared her vulnerability, the Outlander used the phrase "Kneel before the Dragon of Zakuul" to strip the Emperor of his power. With Valkorion weakened, Senya joined her children in the Outlander's mind, and together the family witnessed the Immortal Emperor's final moments and words. Vaylin derived particular satisfaction from using her own trigger phrase against her father, who was reduced to madly ranting on his knees before the Outlander ended his millennia-long existence, liberating Vaylin's spirit.

Simultaneously with the destruction of her father's spirit within the Outlander's mind, Kira Carsen and Lord Scourge located and destroyed Valkorion's original body, from when he was still known as Tenebrae. Upon its demise, the body released a plague that infected Jedi Grand Master Satele Shan and her followers, placing them in a hive mind trance. This plague eventually spawned an entity by consuming the victims. Kira and Scourge sought out the Outlander, who could assist them in eliminating Tenebrae's ultimate weapon. Joined by Arcann and Senya, they entered Satele's mind, where they discovered that the plague's entity was a mental imprint of Tenebrae from before he knew any of them. Many of his victims were also present, although Vaylin sarcastically remarked that she wouldn't be if the Outlander hadn't brought her along. Upon encountering Vaylin and Thexan, Arcann was shocked, while Senya apologized to Vaylin for failing to prevent her father's actions. After his Valkorion persona labeled her foolish, Vaylin unleashed Force lightning upon him, demonstrating that she possessed no more limitations than he did. Joining the other victims of Tenebrae, the family aided the Outlander in destroying this mental imprint, ensuring that he could never return.

Vaylin experienced a relatively typical childhood, filled with laughter and joy as she played with her mother in the woods. However, Vaylin was never truly ordinary, as she exhibited extraordinary strength in the Force even before her birth, to the point where she preferred telekinesis for even the simplest tasks. As she matured, Vaylin developed a fascination with the Force and combat, observing her brothers Arcann and Thexan sparring in the training grounds and attempting similar feats herself. By her teenage years, Vaylin's aptitude with the Force had grown significantly, and she gradually began to change, violently using the Force whenever something upset her, crippling household servants and Knights who served as her sparring partners. Instead of addressing the underlying issue, Valkorion's only solution was to confine Vaylin's mind and powers, effectively suppressing most of her true self.

The time she spent on Nathema profoundly altered Vaylin. Subjected to mental and physical torture to the point of finding amusement in the pain, she became desensitized to the suffering of others, witnessing countless deaths and even deriving sadistic pleasure from their torment. Vaylin blamed her mother for abandoning her, developing an obsession with causing Senya harm above all else, even at the expense of her own power. She maintained positive relationships with her brothers and remained fearful of Valkorion, as his power still surpassed her own, initially unaware that it was the other way around until Valkorion imposed mental restrictions on her. Due to her experiences on Nathema, Vaylin placed immense value on freedom and her own opinions, as those were the very things that had been taken from her there.

Valkorion's absence during the Galactic War allowed Vaylin to experience her true power, but instead of retaliating, she chose to bide her time, siding with Arcann in his coup against their father. As High Justice, Vaylin was merciless towards Zakuulan Knights, indiscriminately killing them for minor mistakes, including her aversion to odd numbers. However, she was pragmatic enough to object to Arcann's order to execute half of all Knights, pointing out that reducing their elite force would diminish their ability to confront the Outlander. When Senya resurfaced after years in exile and allied herself with the Outlander, Arcann found himself fighting a war against his own parents, while Vaylin became consumed with inflicting pain on her mother at any cost, whether through physical torture or the knowledge that Arcann had killed Thexan.

Vaylin committed atrocities with a calm, indifferent demeanor, not to fuel her strength in the Dark side of the Force like Sith, but simply because she could. Nevertheless, she remained close to Arcann, as they both despised the notion of destiny and resented their father for holding them back. After Arcann betrayed her by preventing her from killing Senya, Vaylin felt abandoned by him as well, seizing his throne and hunting her family across the galaxy. Usually fearless and relentless, Vaylin was shocked to learn of Valkorion's ability to suppress her powers, displaying visible fear whenever her conditioning was activated. The apparent encounter with Thexan on Iokath led Vaylin to a brief moment of peace, filled with nostalgia and surprise, before she quickly realized it was an imposter and became enraged by the attempt to manipulate her.

Initially allying herself with SCORPIO because she related to her desire to be free to make her own choices, Vaylin grew increasingly frustrated when the GEMINI captains refused to obey her orders out of self-preservation, eventually finding a way to revert them to their original programming. When breaking free of her restraints on Nathema, Vaylin displayed genuine fear when abandoned by everyone, but refused to die in the place she hated, making her even more dangerous. During the assault on Odessen, she taunted the Outlander by killing their ally in front of them, promising to repeat the act until none remained, prompting the Outlander to strike her down. Post-mortem, however, Vaylin realized that her father was responsible for most of her suffering, and the suffering of others. She found the strength to join the Outlander who killed her, the brother whom she attacked, and the mother whom she hated, in defeating Valkorion, the ultimate evil that had inflicted so much pain on her family and countless others.

Vaylin was the daughter of the Immortal Emperor Valkorion, unaware that the Human's body was inhabited by the spirit of Vitiate, the Sith Emperor who had lived for over a millennium by transferring his essence from one host to another. Vitiate's immense power in the Force was inherited by Vaylin and surpassed even his own, making his daughter one of the few things he feared could challenge him. After Vaylin exhibited extraordinary strength as a child, Valkorion sent her to Nathema, suppressing most of her power and subjecting her to mental conditioning known only to him. Even with these restrictions, Vaylin remained incredibly strong, and she eventually overcame the limits on her power during Valkorion's absence. She was the only known individual capable of resisting Valkorion's time manipulation abilities, breaking free from being frozen in time on the Gravestone and sensing his and the Outlander's spirits in the Eternal Throne room, accurately pinpointing the Outlander to stab them, even without Arcann's awareness.

During her pursuit of the Outlander, Vaylin effortlessly shattered a thick door that Lana Beniko, a Sith strong in the Force, struggled to even lift. Vaylin casually disrupted a massive Sun Generator and was confident in her ability to defeat Beniko and the Outlander even without her lightsaber. Due to her strength in the Force, she was less skilled in lightsaber combat, as noted by her mother during their duels, with Vaylin relying on Force attacks to compensate. Vaylin was the only being powerful enough to survive breaking her chains on Nathema, causing such destruction that beings were vaporized and the shockwave of her power could only be contained by the door of the Emperor's Vault, causing even Valkorion to show fear. With her restraints removed, Vaylin was able to destroy the Sanitarium on Nathema's surface from orbit with apparent ease. During her fight with the Outlander, Vaylin created a massive Force storm, which the Outlander could only resist due to Valkorion's protection, though even the Immortal Emperor was not powerful enough to control Vaylin at this point.

Vaylin appears in the Star Wars: The Old Republic digital expansions Knights of the Fallen Empire and Knights of the Eternal Throne, voiced by Natasha Loring. She serves as a secondary antagonist alongside Arcann in Fallen Empire and becomes the primary antagonist in Eternal Throne, eventually joining forces with the player to permanently eliminate Vitiate after her death. Eternal Throne marks her ascension to the Eternal Throne of Zakuul with a new outfit featuring exposed sleeves that reveal the tattoos she received on Nathema. Vaylin's character is largely unaffected by the player's choices, as most of her appearances are in cutscenes that do not involve the Commander. Vaylin is prominently featured in the Betrayed cinematic trailer, released between the end of Fallen Empire and the release of Eternal Throne, which ends with Vaylin attacking Senya, and continues with A Mother's Hope, a short story by Drew Karpyshyn published on the game's website.
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During Eternal Throne Chapter I: Wrath and Ruin, the player can make a Dark Side choice that leads to the death of Senya Tirall. In this scenario, Vaylin senses her death on Zakuul and becomes enraged at being deprived of the opportunity to kill her mother herself. [32]
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During Eternal Throne Chapter VI: The Dragon's Maw, if Senya was killed, Arcann is not healed and attacks Vaylin for stealing his throne instead of trying to talk her down. Vaylin then witnesses Arcann's death at the Outlander's hand instead of his submission. [35]
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During Eternal Throne Chapter VIII: End Times, the player must choose between saving either Vette or Torian Cadera. The other is captured by Vaylin, who later executes her hostage on the Alliance platform. [3]

- During Eternal Throne Chapter IX: The Eternal Throne, if the player previously made a Dark Side choice to keep Lord Dramath imprisoned in his holocron, he will aid the player in the fight against Vaylin, with Valkorion commenting that his daughter can share the pleasure of killing him. If Arcann was previously killed, his spirit will also be under Valkorion's control alongside Vaylin, attacking the player before being freed by Dramath's holocron. After being freed, Vaylin must be convinced to join the player's side.

- In the Light Side scenario, the options are to let her choose for herself, which Vaylin approves of, to let Arcann remind her of their childhood which Valkorion took away by locking her on Nathema, or threaten to kill her, with Vaylin appreciating the humor and realizing that Valkorion was afraid of her power all this time. In the Dark Side scenario, the options are to remind Vaylin that Valkorion will only cage her again, lie and claim that Senya begged Valkorion to kill the Outlander before dying, causing Vaylin to turn against him out of spite, or assuring Vaylin that Senya suffered and screamed endlessly during her death, which Vaylin enjoys.[7]