Thon was a secretive and often reclusive male Tchuukthai Jedi Master who lived in the period surrounding the events of the Great Sith War. He kept the details concerning his race, homeworld, and origins a closely guarded secret, and possessed extensive knowledge of the Force even in as-yet-unknown techniques. Soon after first visiting the Jedi library world of Ossus, Thon became a Jedi Master, and went in search of a planet where he could live and study in solitude and peace. The Force guided him to Ambria, a planet in the Stenness Node that was plagued by the dark side. After containing the Sith influence to a single spot, Thon settled down and began to take Jedi apprentices, among them Oss Wilum and the future head of the Jedi Order, Nomi Sunrider.
Splitting his time between life on Ambria and communion with the other Jedi Masters on Ossus, Thon often took an advisory role, yet found himself immersed in such events as the Battle of Deneba during the Krath Holy Crusade. Due to his high-profile pupils and his high esteem within the Order, Thon became directly involved in the Great Sith War. Escaping a plot by Dark Lord of the Sith Exar Kun to have the Jedi Masters murdered by their former wards, Thon left Ambria and took a more active role in the conflict. He assisted in the evacuation of Ossus before the planet was devastated by a supernova unleashed by the Sith, and was present at Yavin 4 when Exar Kun made his final stand and was defeated, ending the war. Thon was one of the few Jedi Masters to survive the conflict. A decade after the events of the war, Thon attended the Conclave on Exis Station, where his former apprentice, Nomi Sunrider, discussed the future of the Jedi Order.
Thon's early life was shrouded in mystery. He was a member of the Tchuukthai, a beast-like quadrupedal alien species native to a planet deep in the Unknown Regions, the location of which was kept a closely guarded secret. The Tchuukthai were extremely secretive and reclusive, so information about them and their homeworld was unreliable, at least in Thon's time. The few Tchuukthai who left their homeworld were considered little more than savage beasts by most members of galactic society, until their true intellect was discovered by a Jedi Master, whose name was eventually lost to time. The Jedi befriended Thon on the Tchuukthai's planet, and taught him much about the galaxy. Thon was intrigued at the wonders of the greater galaxy, and eventually the Jedi Master offered to teach his friend in the ways of the light side of the Force. Thon was cautious and unsure about leaving his planet initially; he was afraid that if his species' intelligence was known, they would be ruthlessly exploited by the criminals of the galaxy. However, the Jedi Master agreed to keep the Tchuukthai's intelligence a secret, and trained Thon in the ways of the Force. Thon eventually became a powerful Jedi, and became skilled in a great many Force powers as well as the art of lightsaber combat.
Some time later, Thon arrived on the Jedi world of Ossus, fully trained in the ways of the Force. He gave no indication of where he came from and how he had learned his powers, and so he was of great interest to the Jedi Masters. Virtually no information was known on his species; the Republic Bureau of Xenology had named them the "Wharl" because of the complete lack of information and name on the Tchuukthai. The Bureau sent many inquiries to Thon about his species, though they eventually gave up after Thon continually ignored them. He was a master of every power known to the Jedi, and even taught the other Masters several powers unknown to them at the time. Thon's response to any questions about his origin was always the same: "It is better that you do not know—at least, not yet." The other Jedi accepted this explanation, though it heightened their interest in the reclusive Jedi Master.
Thon eventually became one of the most advanced and revered Jedi Masters of the time, alongside such others as Odan-Urr, Vodo-Siosk Baas, Ood Bnar, and Arca Jeth. Some time during his stay on Ossus, Thon inherited the Jedi holocron, of which Ood Bnar, an ancient Jedi Master who had lived for centuries, was gatekeeper. Bnar was extremely knowledgeable in the history of the Sith and the dark side of the Force, and through the centuries he provided the Jedi Order with the information they needed to fend off these theats. He created a holocron, which was passed down through the generations until it came into the possession of Master Arca, who lent it to Thon.
Thon stayed on Ossus for several years before departing the Jedi planet to search of somewhere more remote to train his students in peace. Thon wore no clothes, and carried only a single item—an ancient lightsaber—as he wandered across the galaxy in his ship, guided only by the Force. One day a place outside the reaches of his ship's sensors, surrounded by dark side energies, caught Thon's attention. For some time, Thon meditated on its presence as the Force guided his ship to the location of the energies. He eventually arrived in the Stenness system, and traveled to the planet Ambria, then known as Stenness.
Thon quickly realized that Ambria radiated the dark side, and sought to find the source. A mineral-rich world once busy with miners, Ambria had never been properly colonized because of its barren, inhospitable landscape. After much of its natural resources had been exhausted, the planet became the home of a Sith sorceress, who, although her name was eventually forgotten, was recorded in the archives of the Jedi Order on Ossus. Using her Sith powers, she constructed a great obelisk infused with the dark side where, once completed, she attempted to conduct an ancient Sith ritual. However, it proved too complex for her to pull off correctly, and she inadvertently released a wave of dark side energy; this eradicated the few sentients living on the planet, further damaged the atmosphere, and tainted the planet with dark side energies. The planet then became a focal point for Sith during the fall of the Sith Empire, who eventually passed away, leaving malevolent spirits behind on Ambria. These energies and spirits remained on the planet for many centuries, until they eventually guided Thon to Ambria.
Thon landed on the surface of the barren planet and was immediately ambushed by the Sith spirits, which he easily repelled with his superior knowledge of the Force. After much time and effort, though, Thon became thoroughly exhausted, and his ability to repel the attackers was diminishing. However, he had devised a strategy to defeat the Sith, and swam out into the middle of a lake, the largest source of water on the planet. When he reached the center of the lake, Thon gave in to the dark side, and the Sith energies swarmed around his limp body. He then cunningly used his remaining energy to use the Force to trap his adversaries in a web of light side energy, before leaving the lake forever. He dubbed the lake "Natth"—meaning "cage" in the Tchuukthese language. The spirits were furious at being trapped under the waters of the lake, and possessed and mutated the local life forms, forming dark side monsters called hssiss. With the exception of Lake Natth, Ambria was finally cleansed of the dark side.
During his wandering on the planet, Thon discovered a meditative canyon located in the Tiernvael Mountains in the northern region of the planet. This area was even more barren than the majority of the rest of the planet, with barely any precipitation and no wildlife. This was largely due to its proximity to the Sith obelisk built by the long-dead Sorceress, though unorthodox weather patterns also affected it. Although the area did enjoy brief times of total calmness, vicious sandstorms usually meant that travel was almost impossible. During one such storm, Thon sought shelter in the canyon, and found that one wall in particular had an unusually powerful connection to the Force. He entered a meditative trance so that he could recover from the injuries he had suffered during the brutal storm, and found that the wall made him feel at ease, unaware of the turmoil around him. He also noticed an array of transparent crystals, which, although they made no impact in the Force, could be used as something to focus on while meditating. The storm eventually subsided, and although Thon left, he made a note of the location of the canyon. He returned there for many years, whenever he was in need of spiritual solace.
Thon built a small training center not far from Lake Natth, and had several breeds of animals transported to Ambria from various worlds throughout the galaxy, in an attempt to bring about the recovery of the desolate world. For over a dozen years, Thon trained several students on Ambria, including a young Vultan named Oss Wilum. Wilum had previously been a student of Jedi Master Garnoo, but when the Neti Master perished, Wilum was left without a tutor. Thon, however, on one of his rare excursions offworld, realized Wilum's Force potential, and brought him to Ambria to complete the Vultan's training. After five years of learning, Wilum had finally completed his apprenticeship, and had surpassed Thon's expectations. The Tchuukthai was surprised at how quickly his apprentice had progressed, considering how late in life he had begun his training. Thon knew that Wilum was ready to join the ranks of the Jedi Knights, and knew that Arca Jeth would be looking for more Jedi to aid him on the planet Onderon, where the Naddist cult was in revolt. He also made arrangements with another Jedi Master, known as Chamma, to have a young Human named Andur Sunrider sent to Ambria to further his training under the Tchuukthai.
Sunrider had learned all that Chamma felt he could teach him, so the ancient Jedi decided to send him to Thon in the Stenness system. Andur was due to arrive on the planet in his ship, the Lightside Explorer, along with his wife Nomi, his baby daughter Vima, and their droid, A-3DO. However, en route to Thon's compound, the trio had been ambushed by thugs sent by the local crime lord, Bogga the Hutt, to intercept them and steal Andur's Adegan crystals, which were to be given to Thon as Master Chamma's thanks for training Andur. During the ambush, Andur had been killed, forcing his wife Nomi to retaliate and slay the assassins with her late husband's lightsaber. After his death, Andur had appeared as a Force ghost to Nomi and urged her to take the gift of crystals to Thon, and telling her that the old Tchuukthai Master would help her decide where to go next. Nomi honored her husband's word, and continued on towards Thon's home. Oss Wilum had yet to depart for Onderon, so he accompanied Thon to meet Nomi, whom they saw standing on a hill overlooking the Tchuukthai's house.
Thon brought Oss toward Nomi, and she originally mistook the Vultan Padawan as the Jedi Master, believing Thon to be a simple beast. Thon did not correct this misinterpretation, keeping silent and acting as if he was indeed an unintelligent animal. Thon and his apprentice led the young woman to the house, providing food for her and her child. As Sunrider began to recount her ordeal, they were soon interrupted when Bogga and his cronies arrived on his sail barge. The Hutt, who had always held a great hatred for Thon, was determined to steal Nomi's extremely valuable Adegan crystals. Thon watched as Wilum attempted to engage the Hutt's men in combat, though the young Jedi could not match their numbers, and was soon captured. Thon then acted, leaping at the men, and using the Force to knock them back. Bogga knew they were unable to match such power and ordered a retreat, though he still did not give up his hopes of acquiring the crystals. It was then that Nomi finally learned that the beast was Thon, and it was he who would be teaching her the ways of the Force.
For the next few months, Thon did not speak a word to his new pupil, allowing her to recover from the grief of Andur's unfortunate death, and to decide the form her life would now take. Nomi, began to doubt Thon, and spent much time pondering his peculiar teaching methods. While Thon was away, Nomi unknowingly used the Force to protect her daughter Vima from the hssiss who populated Lake Natth. In truth, Nomi was using basic battle meditation, though she did not know at the time. Although the hssiss had been defeated, the malevolent spirits in the lake reached out to Nomi and told her she was going to die. Nomi fled the lake, though she still had lingering doubts about Thon, and asked herself why she was on this savage world.
When Nomi returned, Thon finally fully realized her potential, and he knew she would one day become a great Jedi Master. Thon also knew of the great conflicts that would take place in the galaxy, and the role Nomi would play in them—it was then that he decided to begin her training. Oss Wilum had yet to depart for Onderon, and Thon met with one of Arca's apprentices, the Twi'lek Tott Doneeta, who had recently arrived on Ambria to request assistance from the Tchuukthai Master. With Thon's permission, Wilum accompanied Doneeta back to Master Arca on Onderon, finally leaving Thon alone with Nomi Sunrider to begin her training. He told his new apprentice that she would use her Adegan crystals to build a lightsaber, though Sunrider was reluctant to ever use such a weapon again; she had only killed with Andur's saber hesitantly, and was disinclined to do so again. Thon explained that her previous experience with the weapon had been in self-defense, and that she had already shown great skill with the blade. The red-haired Human persisted, noting that Thon did not use a lightsaber, and that she would only accept his tutelage on the condition that she did not have to use a lightsaber. Thon agreed, though he knew she would waver eventually.
Thon decided to take Sunrider to the Meditative Canyon, where her training would begin. He told her that it was not enough for a Jedi simply to know the light; they had to feel the tension between light and dark, both in themselves and in the wider universe. The dark side challenged them, he told her; it made them reach beyond themselves, like when Nomi rescued her child that day. They stopped at Lake Natth, though Nomi wanted to move elsewhere, worried for her child's safety. Thon obliged, and took Nomi and Vima to the edge of the great canyon, which he meditated in regularly. Thon then showed Sunrider his Jedi Holocron, the gatekeeper of which was the ancient Neti Jedi Master Ood Bnar. The tree-like man from Myrkr told them of those who had joined the dark side, and that a mighty conflict between the Jedi and the worshipers of the dark side would happen within Nomi's lifetime. As he pointed at the young apprentice and told her that she would play a pivotal role in the war, Vima became scared, and Thon deactivated the holocron. He told Nomi to take his lightsaber, which he used during his Jedi training. Nomi was frightened by what Bnar's holocron had said, and wanted to leave the planet and start a new life with her daughter Vima. Thon, however, knew what she was thinking, and told her that there was no going back for Nomi Sunrider—there was only going forward, or into darkness.
Meanwhile, Bogga was still determined to acquire the Adegan crystals, and to rid "his" system of Thon, who had proved a thorn in his side one too many times. A local pirate named Finhead Stonebone had incurred Bogga's wrath after raiding an Ithullan ore hauler. The Hutt ordered him to kill Thon as restitution or he would himself be executed. When Stonebone refused, knowing such an attempt on a Jedi Master's life would equal suicide, Bogga had his first mate killed by the Hutt's pet hssiss, forcing Stonebone to reconsider.
Thon and Nomi were traveling back to the training compound when Stonebone and his motley crew, aided by an entourage of Bogga's rough enforcers led by the gangster Gudb, arrived on Ambria in armored skiffs and firing rockets at the building. While Thon was able to use the Force to steer the cannon rounds away from their target, he told Nomi to take up the lightsaber that they might fight the pirates together. Nomi, however, was adamant that she would never touch the weapon again, and apologized to Thon for letting him down. The salvos soon managed to break through Thon's defenses, forcing the Jedi Master to charge the hovering skiffs, terrifying Nomi. Thon attempted to persuade her to use her battle meditation if she would not take hold of her weapon, though she once again refused, telling him that he was the Jedi Master, and that she had to rush Vima to safety. Thon permitted her to, though, claiming that if his apprentice had no power then neither did he—he gave himself up to Stonebone's gang, allowing them to fit him with Mandalorian manacles and to lead him toward their skiffs. Using the Force, Thon telepathically urged Sunrider to use her battle meditation, though she did not want to acknowledge its existence. Finhead Stonebone's men then prepared to lift Thon onto the skiffs.
The pirates entered Thon's compound where they searched for the Adegan crystals, while Nomi contemplated the loss of yet another Jedi. Soon, one of Bogga's enforcers, who had been sent by the Hutt to work in conjunction with Stonebone's crew, found the crystals in Thon's hut. This caused a rift in the ranks of the group of alien criminals, and a massive fight ensued over who would get to present the valuable crystals to Great Bogga. The gangsters' thoughts were being influenced by Nomi, who had chosen by this time to employ her battle meditation. While the thugs fought each other, Nomi took hold of the lightsaber, and finally accepted that she had to use it. She freed Thon and charged at the raiders, aided by the great Tchuukthai Master, who sent bursts of powerful concentrated Force energy at them. Finally, through the efforts of Thon and his apprentice, Bogga's men were defeated, and Stonebone retreated from Ambria. Nomi Sunrider had finally accepted her fate as a Jedi, and Thon began to teach her everything he knew.
After a time, in which Thon had taught his young apprentice all that he could, the ancient Tchuukthai opted to bring Nomi to Ossus to further her training under the Krevaaki Jedi Master Vodo-Siosk Baas, who would begin by teaching Nomi to build her own lightsaber using the Adegan crystals Chamma had intended to be given to Thon. Nomi instantly took a liking to the Jedi training world, noting how peaceful and tranquil the place was. Thon took Nomi and Vima to Master Vodo, who was also training the young Jedi Knights Dace Diath, Shoaneb Culu, and Qrrrl Toq in the art of lightsaber construction. Upon meeting her, Vodo, like Thon and Ood Bnar before him, noted Nomi's strength in the Force, and said that he knew she could become a great Jedi.
Thon stayed with Nomi on Ossus during the several months she trained under Vodo, though she was soon ready to depart with the other young Jedi Knights. Prior to Sunrider's mission to Onderon, Thon brought her with him to the galactic capital of Coruscant to meet with the Republic Ministry of Defense. Speaking in his native Tchuukthese, Thon had his apprentice translate for him a request that the members of the Galactic Senate provide assistance for the Jedi who were beleaguered on Onderon. Thon reminded the senators that the Jedi had fought on the side of the Republic for generations, and that the favor should be returned when necessary. When the senators began to grumble in hesitation, Thon reminded them that if and when the Naddists conquered Onderon, their dark power would sweep across the expanse of the galaxy soon after. This final proclamation swayed the Defense Ministry to commission the full strength of the Republic Navy to join the Jedi in battle. Like Thon's previous student Oss Wilum, Nomi was to travel to Onderon to aid Arca with the Freedon Nadd Uprising. When Nomi departed, Thon returned to Ambria, alone once again.
In 3997 BBY, Thon found himself leaving Ambria once again when as the leaders of the Jedi had called a great convocation of the Order to discuss threat of the Sith-inspired Krath, formed by members of Empress Teta's aristocracy in the wake of the Naddist Uprising. The Krath sorcerers had recently carried out a series of attacks against the Republic, and their growing dark-side menace demanded the attention of all the Jedi. The meeting commenced on the planet Deneba under the leadership of Master Odan-Urr himself and Thon's former apprentice found herself in the spotlight, for she and Ulic Qel-Droma had led Republic forces in battle against the Krath. The Order was unaware that the Krath were preparing to strike again; agents of the dark side had reprogrammed the servant droids used by the Jedi Masters to attack their owners on command, and a vessel packed with combat droids was en route to Deneba.
As the debate over what action to take concerning the Krath carried on, the Krath themselves pressed the attack. War droids descended upon the assembly just as the Jedi's own droids turned on them. The Jedi fought valiantly, employing Arca Jeth's technique of disabling the automatons' internal mechanisms using the Force. The Jedi prevailed in the end, but at great cost of life—Master Arca himself was killed before the battle was won. Following the debacle, Thon returned with many of the remaining Jedi Masters to Ossus as their students set out to address the Krath issue. Ulic Qel-Droma went to the Krath—against the advice of several Masters, including Thon—on a mission to try and infiltrate their ranks that he might end their reign of terror from within.
After months without word from the undercover Jedi, Nomi Sunrider herself—along with Cay Qel-Droma and Tott Doneeta—went to the Krath capital of Cinnagar in order to try and make contact with Ulic. Her mission did not meet with success, however, as she found that Ulic had himself joined the Krath, going so far as to capture Nomi and even to order her death. After narrowly escaping Cinnagar, the three Jedi returned to Ossus to propose another plan. Thon shared his doubts concerning Qel-Droma, stating that perhaps the young Knight was beyond their help; he had made a choice of his own, and may likely even learn the error of his ways without their help. Nevertheless, Thon insisted that they leave Ulic free to decide his own path, consenting to allow his former student to lead another attempt to extract her friend. The plan failed, however, as Ulic Qel-Droma once more chose to remain with the Krath, becoming one of the new Dark Lords of the Sith soon thereafter along with Exar Kun, a former pupil of Vodo-Siosk Baas'.
Thon returned to Ambria and remained there as the war with the Sith began to escalate. Attacks were made on the Republic and the Jedi by the Krath, who were led by Qel-Droma himself, their forces augmented by the armies of Mandalore the Indomitable. Nomi Sunrider accompanied Vodo-Siosk Baas and a group of other Jedi in an attempt to persuade the Republic Senate to let the Jedi handle these matters, but it was too late; the Krath attacked Coruscant itself, with Ulic Qel-Droma at their head. The Jedi and the Republic were victorious when Qel-Droma was betrayed and abandoned by his lieutenant and lover, the Tetan sorceress Aleema Keto, in an effort to take control of the Krath from him. The traitor himself was captured due to his underlings' treachery, and was slated to stand trial for his actions.
Meanwhile, Exar Kun was recruiting more young Jedi to his cause, which he misrepresented as a new Jedi Order, its teachings supplemented by knowledge that the Jedi Masters, he alleged, had kept from their students—Sith knowledge. After killing Master Odan-Urr in order to procure a Sith holocron which the Jedi historian had been keeping safe, he used the item as "proof" of the hidden knowledge; knowledge he promised would bring about a new golden age for the Jedi. Among the young Jedi Knights to accompany Kun from Ossus to his base on Yavin 4 was Thon's former apprentice, Oss Wilum. Although Wilum himself had more doubts than the rest concerning Kun's knowledge and intentions, the new Dark Lord of the Sith used dark side magic to enthrall the group, possessing them with Sith spirits.
Ulic Qel-Droma stood trial before the Senate, and Nomi Sunrider, along with Ulic's brother Cay and the Cathar Jedi Sylvar, attended. The proceedings went horribly wrong as Qel-Droma, instead of answering for his crimes, spoke out against the Republic and the Jedi. Exar Kun himself came to rescue Ulic from the tribunal, murdering the Supreme Chancellor of the Republic and slaying Master Vodo in the process. Nomi Sunrider, dejected, decided to visit Thon on Ambria in order to get away from the war. Sylvar accompanied her.
Another of Thon's former students was planning to visit his master: Oss Wilum, now the unwitting servant of Exar Kun. Accompanied by Crado, the mate of Sylvar and another of Kun's minions, Oss was sent to Ambria to kill Thon, in a wider plot by Kun to kill off the Jedi Masters of the Order. As Nomi Sunrider, her daughter Vima, and Sylvar were arriving at the home of Thon, Oss Wilum and Crado were at Lake Natth, preparing to kill the Master. The pair summoned the monstrous hssiss from the lake using Sith magic, and started off in the direction of their objective.
Sensing the disturbance, the three Jedi rushed to head off the attack. Nomi and Sylvar lashed out at the hssiss with their lightsabers—but Thon threw himself at the beasts, tearing at them with tooth and claw. The hssiss were all but defeated once Sunrider employed her talents with battle meditation to distract them that Thon might finish them off. Sylvar and Thon quickly turned their attention to Oss Wilum, knocking him down and freeing him from his Sith-induced trance. After a short confrontation in which Sylvar condemned her mate for his actions, Crado fled, and the three Jedi helped an injured Wilum into the house. Thon managed to bring his fallen pupil back to the light, though the Tchuukthai Master never fully recovered from the pain of betrayal. He feared for the other Masters, only to discover later that his fears had come to fruition: the minions of Kun had succeeded in killing all of their Masters, and only Thon had escaped their doom.
Thon and the three Jedi—along with little Vima—returned to Ossus to meet with the Order concerning the growing crisis. As Thon and Nomi Sunrider discussed the fall of Ulic Qel-Droma and the murders of the Jedi Masters with a number of other Jedi, Tott Doneeta rushed in with news: the Sith were attacking once again. The space station known as Kemplex Nine, which was located in the Cron Cluster of the Auril sector, was under siege by a Sith vessel of ancient origins. Thon recommended caution; the station itself was not an important military target, and he suspected that the Sith were staging a feint. As Ossus was both nearby and of much more import, it would be a more desirable target, and so the Jedi decided to split their forces. Jedi Shadows Dace Diath, Qrrrl Toq, and Shoaneb Culu volunteered to lead a fleet to counterattack at Kemplex, while Thon and the rest of the Jedi remained on Ossus to safeguard the library world.
The attack did indeed turn out to be a false move on the part of the Sith, but not as the Jedi had suspected. The ancient Sith battleship, commanded by Crado and Aleema Keto, drew the Jedi and Republic forces out, leading them on a chase into the Cron Cluster. There, Aleema used Sith magic to rip out the core of one of the cluster's stars, destroying the Jedi fleet. The reaction went out of control, causing an implosion of the core and subsequent supernova, killing Crado and Aleema and unleashing a massive stellar shockwave. Ossus was in the path of the explosion, and had very little time left before the devastation reached it.
As the shockwave bore down on the planet, the Jedi rushed to evacuate all living beings—and as many precious records and artifacts as possible. As the remaining inhabitants of Ossus made their hurried choices of what to take or leave, Thon and his companions grew devastated at the planet's impending doom. As they headed for their transports, Cay Qel-Droma felt a presence above: Ulic was arriving on the planet, along with Sith and Mandalorian forces that Exar Kun had brought to plunder Ossus before it could be destroyed. Cay flew off in the Nebulon Ranger to meet his brother.
Exar Kun landed and immediately headed for the libraries, where he could take as much valuable Jedi information as possible. He entered a chamber where Ood Bnar was working to place artifacts and scrolls in a shielded vault before leaving, and the two did battle. As Kun's Sith Massassi warriors came to their master's aid, Bnar saw that he could not fight them off, and so he forced himself into his species' metamorphosis, turning himself into a stout tree in order to prevent Exar Kun from taking the relics. However, he rendered himself immobile in the process, joining his fate to that of the planet.
As the evacuation continued, Thon noticed the attackers' ships in the air. Among them was the vessel of Ulic Qel-Droma, as well as the Nebulon Ranger, being flown by Cay; the ships were falling from the sky. Tott Doneeta and Nomi Sunrider raced off to aid them, leaving Vima in Thon's care. Arriving at the crash site, Nomi marked a grim scene: Ulic had just killed his own brother. That Qel-Droma might never again do harm with the dark side, Nomi used a little-known ability to cut Qel-Droma off from the Force completely.
Thon, Vima, and Oss Wilum soon arrived, and discovered all that had transpired. The Tchuukthai Master told everyone to get to their ships, and then went off on a final errand on Ossus—he had to say goodbye to Ood Bnar. Thon came upon Bnar in tree-form atop the shielded vault, and expressed his sadness for Ood's sacrifice. Bnar reassured him that he had accomplished his goal, and that he might not even die in the upcoming cataclysm. The two said their goodbyes, and Thon returned to his ship, leaving Ossus behind forever. The shockwave arrived soon thereafter, utterly devastating the planet.
In the only chance he had to at least partially redeem himself for his actions, Ulic Qel-Droma led a Jedi and Republic fleet to Exar Kun's home base on Yavin 4. Thon accompanied the fleet in his personal transport. Knowing that he could no longer defeat the forces arrayed against him without his allies, Kun employed Sith magic to secure another escape. Drawing upon the life-force of the entire Massassi race on the moon, he freed his spirit from his physical body, giving himself a form of immortality. Realizing that he was still a threat without corporeal form, Nomi Sunrider used the Force to bind Kun's spirit to the planet, that he might not escape into the greater galaxy. The Sith War was over, and the Jedi had won, but not without paying dearly for their victory.
Following the events of the Great Sith War, the Republic—and the Jedi along with it—slowly recovered. Nomi Sunrider, Thon's former apprentice, grew in renown, and was named head of the Jedi Order. A decade after the end of the war, it was decided that a conclave would be held on Exis Station in the Teedio system, as the Order had not met in substantial numbers since the great convocation on Deneba during the Krath crisis. Arriving on the station, Thon was delighted to see Vima Sunrider, now a young teenager, who had accompanied her mother to the conference. He was also greeted by Sylvar, who had grown more bitter in the years since the war despite her hero status, but nonetheless Thon was happy to see her as well.
The conclave began, led by Nomi Sunrider, who spoke of the horrors of the war—and the healing that had taken place since. As his dear friend and former student spoke, Thon noted that she had become a great Jedi, and that the rest of the Order held her in high esteem. The speech was cut short, however, as Nomi, Sylvar, and Thon felt a disturbance in the Force. It was Vima; she was in danger.
The teenage girl, bored with the conclave and frustrated with her mother's neglect of her Jedi instruction, had slipped away and stolen one of the ion mining ships in the station's hangars. She had soon lost control of the vessel as it became caught in one of the nearby star's magnetic loops. The assembled Jedi were all but helpless as Vima punched out of her vehicle before it could careen into the star. She was not out of danger, however; the miners' foreman refused to risk more ships retrieving her escape pod before it, too, might fall into the inferno. Vima was rescued when the escape pod was grappled by the ship of Tott Doneeta, who was late arriving to the conclave.
With Vima safe and back on the station, the meeting continued. Sylvar spoke next, of Ulic Qel-Droma. The former Sith Lord had been living in self-imposed exile since the Sith War, though he was technically a war criminal. Cut off from the Force, he wandered from planet to planet, trying to find somewhere to live out his days in solitude. Sylvar did not agree with this, blaming Qel-Droma for the atrocities of the war, and wished that the man no longer be allowed to walk free, but rather that he be punished for his crimes.
On this note, the convocation ended. Sylvar went with Tott Doneeta to Ryloth, while Thon remained on Exis Station with Nomi Sunrider. Yet once again, Vima was nowhere to be found. The girl had stowed away aboard a ship and traveled to the frozen planet Rhen Var, where Ulic Qel-Droma was living in seclusion. Having less negative memories than her contemporaries about the man, she hoped to convince Ulic to train her in the Jedi arts. After a thorough search of Exis Station, Thon informed Nomi that her daughter was nowhere to be found, and was not likely on the station at all.
Nomi resolved to find her daughter and traveled to Rhen Var alone, but not before the girl had received a substantial amount of training from Qel-Droma. Sylvar, however, was also on the planet, having come with the spacer Hoggon, who had brought first Ulic and then Vima to Rhen Var. As Nomi spoke with her daughter, Sylvar confronted Qel-Droma, and the two fought. In the end, though Sylvar would not kill Qel-Droma when he was unarmed and unwilling to fight back, the fallen Jedi was killed by a blaster bolt fired by Hoggon, who wished to earn a place in history for himself. The three Jedi left Rhen Var, and Nomi Sunrider took Vima as her apprentice to finish the girl's training.
Thon's name, and the legends it was attached to, continued to be well known for thousands of years. He appeared in the stories of Ulic Qel-Droma and Nomi Sunrider that were contained in the Tedryn holocron and delineated by Bodo Baas, a descendant of Thon's contemporary, Vodo-Siosk Baas. The Master's Force talents were recounted by Beldorion, a Hutt Jedi who admired his abilities. Tionne Solusar, a Jedi historian who lived thousands of years after the Sith War, composed a ballad celebrating Thon's most famous apprentice. Solusar, having dedicated her life to the study of legendary Jedi, was well-versed in knowledge concerning the people Thon knew in his lifetime.
Thon's work on Ambria eventually came to fruition, and over several centuries the barren planet began to recover. The dark side spirits contained in Lake Natth, however, would plague the planet for evermore. In later eras, the meditative canyon discovered by Thon became a haven for Jedi seeking refuge, and during Palpatine's Great Jedi Purges, many Jedi used the canyon as a hideout.
Though he was famous as a Jedi Master and trained many students, Thon lived simply while on Ambria, maintaining a humble dwelling near Lake Natth. During the training of Oss Wilum, the two Jedi cared for a herd of the staga native to the planet. Although Thon possessed a lightsaber, which was his only possession when he arrived on Ambria, and even a set of Jedi robes, he was not known to travel with such trappings of the Jedi for much of his life, which he spent in seclusion with his students.
The Tchuukthai typically spoke in short bursts, often inserting phrases from his native language. However, he could speak at length on subjects of import, and Thon was also known to be and was quite eloquent on occasion. He often expressed himself and taught lessons in a profound manner; when Nomi Sunrider first arrived on Ossus, Thon pretended to be a simple beast under the care of Wilum, and after she learned his identity, he did not speak to her for months, allowing her to grieve her husband's death. However, Thon could be a warm and caring creature as well. He was often involved in the upbringing, care, and initial Jedi training of Vima Sunrider when she was a child, and even wished that she would give him a hug when they were reunited on Exis Station. Conversely, if the situation demanded it of him, he took a hard line. When attempts to rescue Ulic Qel-Droma from the Krath and turn him back to the light were discussed, Thon was opposed to the idea, stating that perhaps Qel-Droma should learn from his mistakes without the aid of the Jedi. Thon was not as dispassionate as Jedi of later eras; when his friend and colleague Ood Bnar essentially sacrificed himself to protect Jedi knowledge from Exar Kun, Thon made sure to visit him before leaving Ossus, showing sadness as well as respect for the Neti Master's decision.
As a Tchuukthai, Thon possessed considerable natural means of defending himself. He was large and well-muscled, and more than capable of carrying adult humanoids on his back. A bony frill around his neckline, armor plating on his back, hornlike projections from his jaws, and spikes protruding from his shoulders helped to protect him from harm. Each of Thon's four legs ended in a set of sharp, strong claws, ideal for slashing. Additionally, the Tchuukthai had strong jaws filled with long, sharp teeth, which he used to considerable effect on the hssiss of Lake Natth.
When he first came before the Jedi Masters on Ossus, Thon already had extensive knowledge of Force techniques, including some that the Masters themselves did not yet know of. By the time Nomi Sunrider came under his tutelage, Thon was possessed of a myriad of Force powers. He was capable of telepathic communication, as he showed after he allowed himself to be captured, when he used the Force to tell Nomi to use battle meditation. The Tchuukthai was himself capable of battle meditation, but Vodo-Siosk Baas stated that Thon was not as talented in it as Arca Jeth. Furthermore, Thon brought Nomi Sunrider to Ossus to refine her talents in battle meditation with Odan-Urr, who possessed greater knowledge of the technique than he. Thon was a Jedi Weapon Master, and although he was capable of wielding a lightsaber, when it came time for Nomi to build her own weapon, he brought her before Vodo-Siosk Baas for instruction in the matter.
Upon arriving on Ambria, the Jedi Master at first had little difficulty in defeating the dark side spirits that lurked there, and when he grew weary, he cunningly "played possum" in order to lure them in. He then used his considerable abilities in directing light-side energy to contain the Sith apparitions fully. Furthermore, when Bogga the Hutt's thugs attacked Nomi and Oss Wilum, Thon was able to use massive waves of Force energy to knock them down. Later, as Finhead Stonebone and his gang attacked Thon's home from their skiffs, the Master deflected their salvos with a wall of Force energy. The Tchuukthai was later said to have possessed the ability to use the Force to create light itself.
Millennia after their deaths, both Thon and Nomi continued to be classed as among the most powerful Jedi Masters of all time; indeed, the Hutt Jedi Beldorion seemed to believe that the pair, along with Grand Master Yoda, to have had unparalleled skill in the light side of the Force.
The character of Thon was created by writer Tom Veitch, and was first mentioned in the endnotes of the comic book series Star Wars: Dark Empire. Thon was first depicted in Tales of the Jedi 3. He continued to appear in subsequent issues throughout the rest of the Tales of the Jedi series, where his character was further developed by Veitch as well as Kevin J. Anderson. Author Drew Karpyshyn mentions Thon in conjunction with Ambria in the third novel of the Darth Bane Trilogy, titled Darth Bane: Dynasty of Evil. Thon is mentioned directly only in one novel set in the New Republic era, but Nomi Sunrider and "her Master" are referred to in several others. Thon receives a brief mention in the video game Star Wars: Knights of the Old Republic II: The Sith Lords, where the player can attain a Jedi robe which supposedly belonged to the Tchuukthai master.