Dorjander Kace, a Jedi Master of the Human male persuasion, found himself a prisoner of the Mandalorian Crusaders during the Great Sith War, remaining in their custody for the duration of the conflict. While held captive, he developed feelings for a Mandalorian woman named Varda. The couple was expecting a child when Varda tragically perished in a Republic bombing raid carried out by a Jedi. Despite the profound grief caused by this loss, Kace returned to the Jedi Order after the war, where he distinguished himself and eventually earned a position on the Jedi High Council. As the Mandalorian Wars erupted and Jedi Knight Revan began advocating for the Jedi Order's involvement, Kace strongly opposed the idea. However, the Council ultimately approved Revan's participation, leading Kace to resign from his Council seat. Convinced that the Republic was irredeemably corrupt, Kace became certain that the Mandalorians would inevitably triumph. He came to believe that the Mandalorians, guided by the Jedi Order, would provide a superior governance for the galaxy compared to the Republic.
Kace gathered a group of Jedi Knights who shared his views and formed a faction known as the Mandalorian Knights, secretly defecting to the Mandalorian cause. His aim was to aid his new allies by providing them with their own Jedi Knights. To achieve this, Kace devised a scheme to infiltrate the Jedi Enclave on the planet Dantooine. By leading a Republic military unit called the Phaeda Militia in an attack on the planet Essien, Kace successfully deceived Captain Dallan Morvis and the troops under his command into abandoning their ship, the Axehead frigate Reciprocity, without a sufficient guard. Seizing the frigate and compelling the Phaeda Militia to serve under his command, Kace utilized the Reciprocity to reach the Jedi Enclave.
Upon arriving at the Enclave, he locked down the academy staff and made preparations to remove the Jedi Trainees from the planet. However, his plans were thwarted by former Jedi Padawan Zayne Carrick and the Phaeda Militia, who successfully rescued the Jedi children from Kace's grasp. The founder of the Mandalorian Knights refused to yield and engaged in a duel with Carrick inside the Enclave. Kace ultimately relented when his obsession nearly drove him to kill one of his own soldiers, the technician Koblus Sornell, who was pregnant. Reminded of Varda, Kace released the captured Enclave staff and surrendered to Jedi Master Zhar Lestin. He was subsequently transported to Coruscant, the galactic capital, where he and the Mandalorian Knights faced a public trial for treason against the Republic. Even during the trial, Kace remained steadfast in his convictions and used the opportunity to present his cause to the assembled crowd.

During the era of the Old Sith Wars, Dorjander Kace, a Jedi Master who was a male Human, was an active participant. In the course of the Great Sith War, Kace fought alongside the Galactic Republic against the forces led by Exar Kun, the Dark Lord of the Sith, and his Mandalorian allies. At some point during the conflict, the Mandalorian Crusaders took him prisoner, forcing him to live among them in captivity. While living among the Mandalorians, Kace developed a romantic relationship with Varda, one of their own, who imparted to him the traditions of her people, leading Kace to willingly embrace the Mandalorian way of life. Varda became pregnant with Kace's child, but she met her end in a Republic bombing raid conducted by a member of the Jedi Order. Kace was overwhelmed with grief, believing that Varda's death at the hands of a Jedi was unjust and that she deserved a fair fight against the Republic, rather than against its Force-wielding servants. When the war concluded in 3996 BBY with the defeat of Kun and the Mandalorians, the grieving Kace returned to the Jedi. In the following decades, he served with distinction, even attaining a position on the Jedi High Council.
Twenty years after the Great Sith War's conclusion, the reorganized Mandalorians initiated their second conquest of the galaxy. For a period of ten years, the Republic permitted the Mandalorians to roam freely through the Outer Rim Territories, seizing worlds that were outside of Republic jurisdiction. Finally, in 3966 BBY, the Republic responded by granting Taris, a world in the Outer Rim, membership in the Republic and establishing a defense against a potential Mandalorian attack. Over the subsequent two years, the Republic and the Mandalorians engaged in a series of minor skirmishes in the region. Following these battles, the charismatic Jedi Knight Revan began to actively campaign for the Jedi Order's intervention in the conflict. The Council hesitated to accept Revan's proposal and become entangled in another conflict so soon after the devastating Great Sith War, and Kace was the most vocal opponent of the Jedi's involvement among all the Council members. Nevertheless, Revan's cause gained support within the Order, and his group evolved into a fully-fledged Revanchist movement. Consequently, Kace's strong stance against involvement was not well-received by the Republic, leading them to find a way to force him to step down from the Council and be replaced by Master Lucien Draay.
Having become disillusioned with a Republic he perceived as corrupt, Kace held the firm belief that it was beyond redemption and would ultimately lose the war, even if it took decades for that to happen. Conversely, he believed that with the Jedi Order's guidance, the Mandalorians could be steered away from their violent tendencies and become the sole hope for a brighter future for the galaxy. To that end, Kace devised a plan to expedite the Mandalorian victory by leveling the playing field and equipping the crusaders with their own Jedi Knights. Gathering a group of Jedi Knights who shared his convictions, Kace established a clandestine organization known as the Mandalorian Knights and secretly pledged his allegiance to the Mandalorians. Keeping his true motives concealed and remaining within the ranks of the Jedi Order, Kace volunteered to join the Revanchist movement. He led his disciples to the front lines of the war, intending to eventually reveal his true allegiance and commandeer a Republic vessel. The Jedi Master then planned to use the captured ship to infiltrate the Jedi Enclave on the planet Dantooine and abduct the Jedi Younglings in order to raise them among the Mandalorians and transform them into new Mandalorian Knights. Mandalore the Ultimate, the leader of the Mandalorians, agreed to allow Kace and his Knights to keep the abducted children once the operation was complete and permitted them to establish a training center on the planet Ordo. Mandalore then assigned a detachment of his warriors to assist Kace and instructed them to follow the Jedi's commands.

In 3962 BBY, Kace initiated his plan by leading Republic troops in an attack on the planet Essien, which had recently been occupied by Mandalorian forces. As the Republic lacked a regular army, it relied on local militias to fight the war. Under Kace's command was the Phaeda Militia, a regiment composed of beings native to the planet Phaeda who had been drafted into military service by the Republic. The militia operated from the Axehead frigate Reciprocity, commanded by Captain Dallan Morvis. The militia's supposed target was the Mandalorian bastion established under Mount Savage, a mountain located on an island. After landing on the planet, Kace and his Mandalorian Knights took speeder bikes and, under the guise of leading the charge against Mandalorian defenses spread across the island's beach line, rode away, leaving Morvis and his militia to fight the Mandalorians as they approached the beach. After putting up a significant fight to maintain the illusion of the island's defense, the Mandalorian forces retreated, although they suffered casualties when Morvis refused to cease fire at the beach, hoping to completely annihilate his enemies. Kace and his Knights then returned to Morvis's position, only to witness the Captain arguing with a member of the militia, Zayne Carrick, who opposed the decision to fire on the retreating enemies. Claiming that his Knights had secured the beach, Kace falsely informed Morvis that the remaining Mandalorians had retreated into the forest surrounding Mount Savage. The Jedi Master told Morvis that his men would lead the attack on the mountain, but they would need the Phaeda militia to root out the Mandalorians in the forest. Instead, Morvis suggested using their supply of the Tibanna-six substance to burn the forest to the ground and kill all of their enemies. That once again raised Carrick's protests, but Kace agreed with Morvis's plan and instructed the Captain to bring every crew member from the Reciprocity for the attack, claiming that there were prize vessels available for capture at the Mandalorian base.
As night fell, Morvis and his men headed toward Mount Savage, using Tibanna-six to devastate the forest ahead of them. Having done so, the Republic troops discovered piles of scorched Mandalorian armor, leading them to believe that there were no survivors of the Tibanna-six attack. However, the Mandalorians had never been present in the forest, and the armor had been strategically left there to deceive Morvis and his troops. Carrick uncovered this deception, having ventured into the forest before the attack in an attempt to warn the Mandalorians of the Republic's intentions but finding no one there. Carrick's discovery did not aid the Phaeda militia, as Kace and the Basilisk war droid–mounted Mandalorians surrounded them. Having captured the Reciprocity, Kace revealed his true allegiance to Morvis and informed the members of the Phaeda Militia that they had been forcibly drafted into the ranks of the Mandalorians. The next step in Kace's scheme was the deactivation of Republic transmitter stations en route to Dantooine, in order to sever the Jedi Enclave's contact with the Republic. The first of these stations was located on the planet Halthor. Using the Reciprocity, Kace's Mandalorians and the newly recruited Phaeda Militia reached the planet. Upon sighting the Republic ship, the Halthorians deactivated the planet's defense shields and allowed the Reciprocity to land. The transmitter's defenders were caught by surprise as Kace and the Mandalorian warriors disembarked from the ship and attacked the station. After a brief battle with Halthorians, the transmitter was captured, and the Mandalorians quickly established a camp on the planet.

Following the fight, Kace delivered a speech to the Mandalorians, acknowledging their reluctance to accept Force-users into their ranks. He assured his followers that his reason for joining the Mandalorians was to teach the Republic the ways of the Mando'ade, citing the female Devaronian communications technician Koblus Sornell as an example of the true Mandalorian way, highlighting her determination to fight for her people while raising her son Gheedor alongside her husband Haarm. With Halthor secured, Kace prepared for the next phase of his plan—attacking Phaeda. To accomplish this, Mandalore agreed to dispatch three Kandosii-type dreadnaughts staffed with over a hundred thousand warriors to assist Kace's troops. The night after the conquest of Halthor, Kace witnessed his men detaining Morvis, who had attempted to kill Ko Sornell in her sleep. Morvis was then placed under guard alongside the other members of the militia. Also present at the scene was Carrick, whom Kace recognized as the rogue Padawan of Master Lucien Draay. Two years prior, Carrick had been falsely accused of perpetrating the Padawan Massacre of Taris and had been forced to flee from the Jedi Order, employing various ruses and schemes until his name was cleared. Refusing to be reinstated as a Jedi and returning to his homeworld of Phaeda, Carrick had been drafted into the militia and placed under Kace's command for the attack on Essien. Kace and Carrick engaged in a conversation, with Kace revealing to the former Padawan his intention to attack Phaeda. As the three dreadnoughts arrived at Halthor, Kace, recognizing Carrick's talents for subterfuge, presented the latter with an ultimatum—either he would witness the destruction of his homeworld and the death of his family who resided there, or he could devise a plan to sever Phaeda's connection with the rest of the galaxy without resorting to an all-out assault.
In an effort to spare his planet from annihilation by Kace's forces, Carrick indeed conceived another idea. He proposed using the Reciprocity to infiltrate Phaedacomm, a high-security space station managed by Bith and located on the outskirts of the Phaeda system. As Phaedacomm handled all signal traffic for Phaeda and connected the planet to the rest of the galaxy, holding the station for a few days would satisfy Kace's need to shut down Phaeda's communication with Dantooine and provide the commanders of the dreadnoughts with certain information they required to follow Kace to Dantooine. Proceeding with Carrick's plan, Kace and a strike team of Mandalorian Knights and warriors took the Reciprocity to Phaeda. As they approached the planet, they were intercepted by the Phaeda Planetary Defense Force cruiser Derapha. Because there had been no word from the Reciprocity since the battle on Essien, the Derapha refused to allow the ship to approach Phaeda without speaking to Captain Morvis. However, Carrick responded to the cruiser's hails, claiming that he was the only surviving crew member, as Morvis and the rest of the militia were in sick bay after being exposed to an unknown biological weapon used by the Mandalorians on Essien. Kace then intervened, stating that he and his Jedi were unaffected, but Carrick required immediate medical attention. Fearing the release of the unknown disease on Phaeda, the Derapha forbade the Reciprocity from landing but instead directed the Republic ship to Phaedacomm, which possessed a medical station with a quarantine area, just as Carrick had planned.

After docking with Phaedacomm, Kace and his Knights delivered Carrick and the Mandalorian strike team inside the medical facility, using sealed biohazard-containment bags and falsely claiming to the Bith station operators that the bags contained the infected members of the Phaeda militia. Before the bags could be delivered to the quarantine area, Carrick, wearing makeup to make him appear infected, broke out of his bag, calling for help. According to Carrick's plan, the Bith would have no choice but to quarantine the entire station or risk the disease spreading. However, the Bith opted to evacuate the facility instead. Kace attempted to use a mind trick to persuade them to stay, but at that moment, the Mandalorians, led by the Togorian Rally Master Kra'ake, broke free from the containment bags, tired of waiting and acting discreetly. Kra'ake and his men opened fire on the Bith, leaving Kace and his Knights with no option but to join the fight. As a result, all of the Bith were killed, and a fight erupted between Carrick and Kra'ake, the former angered by the unnecessary killing. Kace intervened to stop their fight, explaining to Carrick that the Mandalorians were warriors by nature and had already been pushed to their limits with all the subterfuge. Kace deemed the mission a success and congratulated Carrick on saving his home planet from invasion, assigning Ko Sornell to watch over the former Padawan. With Phaedacomm under Kace's control, the Jedi Master gained access to information he hoped to learn on Phaeda and provide to the dreadnaught chiefs. Kra'ake then departed for Halthor to deliver the information.
Shortly afterward, Kace was confronted by Carrick, who had managed to uncover a file that the Republic Ministry of Defense had been keeping on the Jedi Master since the Great Sith War, thus learning about Kace's time in captivity. Carrick also traced Kace's attacks, deducing that the next target was Dantooine, although he believed that Kace intended to kill the trainees there. Kace then revealed his true goal to Carrick, sharing his story about Varda and his views on the Republic, the Mandalorians, and the war. The Jedi Master attempted to persuade Carrick to join his cause, but when the latter refused, he ordered Sornell, who was supposed to remain in charge of Phaedacomm, to lock the former Padawan inside the station's quarantine area, hoping he would change his mind by the time Kace returned with the younglings. Rallying his Knights and Mandalorian warriors aboard the Reciprocity, Kace delivered a final motivating speech before they embarked on their mission. He was also surprised to find Sornell aboard the Republic ship; the Devaronian claimed that the Jedi Master would need his best warriors during the operation. Upon entering the Reciprocity's bridge, Sornell punched the technician who had been tasked with monitoring all communications with the dreadnaughts, knocking the man unconscious and justifying her action by stating that he had cheated her in a bargain sixteen years ago. Admiring the woman's spirit, which reminded him of Varda, Kace allowed her to stay and assigned her to take the unconscious technician's station. Unbeknownst to Kace, Sornell had volunteered for the mission to sabotage it. Having come to respect Carrick after he had saved her and Gheedor's lives on Essien, Sornell had released him instead of locking him up as Kace had ordered.
When the Reciprocity reached Dantooine, it was intercepted by a squadron of Aurek-class tactical strikefighters from the local security force. However, upon Kace introducing himself, one of the Enclave's Masters, Zhar Lestin, recalled the starfighters, apologizing to Kace and stating that they were unaware of his arrival, as Dantooine's communications with Phaeda and the Core Worlds were down. Continuing his deception, Kace claimed that the communications problem was the exact reason for his arrival, stating that the Republic had sent him to reinforce Dantooine's military force until the issue was resolved. Lestin believed Kace's story and allowed him to proceed. Before landing, Kace asked Sornell to contact the dreadnaughts and inquire if they were following as planned. The Devaronian replied that they were, although she had actually received messages that the dreadnaughts' approach had been halted due to a "Jedi Brain Fever" outbreak aboard the lead dreadnaught Parjai. The "Jedi Brain Fever" was, in reality, a ruse created by Carrick, who had returned to Halthor, liberated the members of the Phaeda militia, infiltrated the Parjai, and forced its crew to abandon ship by pretending to be infected with a dangerous disease. Unaware of these events due to Sornell's lies, Kace gave his troops the signal to land on Dantooine.

Once there, Kace's soldiers corralled the Enclave's personnel and students. Kace gave the order to his troops not to employ blaster weaponry, fearing injury to the younglings. Initially, the instructors resisted, with Lestin engaging Kace in a lightsaber duel. However, upon observing one of Kace's dreadnoughts' arrival, Lestin understood the battle was lost, and he and his subordinates surrendered. Kace's forces confined Lestin and the remaining staff within the local Jedi Council's assembly hall. Kace, attempting to appear amicable towards the Jedi children, informed them that they would soon join the Mandalorian ranks, and a Shaadlar-type troopship touched down near the Enclave to transport the trainees to the dreadnought hovering above the planet's surface. Kace and his Mandalorians escorted the Jedi children to the troopship, where they encountered a Mandalorian squad commanded by a Field Marshal who identified himself as Glomkettle, the commanding officer of the dreadnought Parjai in orbit. The Field Marshal stated that the other two dreadnoughts were experiencing delays and reassured Kace that the Parjai was prepared to receive the Jedi children. Kace, judging that the Reciprocity had fulfilled its purpose and that diverting troops to transport it to Mandalorian territory would be imprudent, suggested its destruction.
The instant Kace brought up the Republic vessel's destruction, he noticed one of Glomkettle's Rally Masters exhibiting a conspicuously horrified reaction, leading Kace to suspect that the Rally Master was actually Captain Morvis in disguise. Glomkettle then announced to Kace that the Mandalore had supposedly tasked Kace's Knights with a new, confidential mission that would necessitate further use of the Reciprocity, while the Jedi children were to be transported to Mandalorian territory aboard the Parjai. Nevertheless, Morvis inadvertently exposed his deception by responding to a greeting from Kace, and the Jedi Master commanded his troops to isolate the newly arrived Mandalorians—the members of the Phaeda militia—from their troopship. Simultaneously, the Jedi Master apprehended Morvis and "Glomkettle," or rather Carrick, taking them into custody and ordering Carrick's soldiers to surrender. Revealing a contingency plan, Carrick remotely activated the troopship's self-destruct mechanism, detonating the vessel and throwing Kace to the ground. Amidst the resulting pandemonium, the Reciprocity crew evacuated the Jedi children onto the frigate and departed. Refusing to yield, Kace engaged his jetpack and soared towards the Republic vessel, lightsaber activated. Carrick intercepted him mid-flight, utilizing his own jetpack to collide with Kace. The two men crashed through the Enclave's transparisteel rooftop, landing inside the Jedi Council chamber, much to the astonishment of the academy staff still restrained there. Following a brief confrontation, Kace kneed the former Padawan in the abdomen and once again attempted to fly towards the Reciprocity, but Carrick prevented him. Sornell then entered the chamber, intending to halt the conflict, stating that assimilating orphaned children into the Mandalorian way was one thing, but forcibly abducting them was unacceptable for a Mandalorian. The Mandalorians had opposed the plan from the beginning, but they were compelled to obey Kace due to the Mandalore's orders. However, the Mandalore had now reneged on the agreement, recalling the other two dreadnoughts after Carrick's actions on the Parjai, which resulted in the ship's destruction. The remaining Mandalorians who had accompanied Kace were also departing Dantooine.

Incensed by the unraveling of his plan, Kace prepared to kill both her and Carrick. However, Sornell informed the Jedi Master that she was expecting another child, and Carrick, reminding Kace of Varda, questioned whether he was willing to perpetrate the same act that the Jedi had committed against Varda and her unborn child. Convinced that his plan had been flawed from the outset, Kace deactivated his lightsaber and released Lestin and the other instructors. Taken into custody by Lestin to be tried for treason against the Republic, Kace requested only one thing from the Jedi Master—to allow Sornell to return to her family. Kace and the remaining Mandalorian Knights were transported to the galactic capital of Coruscant and stood trial before a large audience, with Minister of Defense Koa Delko serving as the prosecutor in the Senate Hall. Even there, Kace persisted in his ambition to convert the Jedi to the Mandalorian cause, proclaiming from his platform for nine hours the righteousness of his cause. Despite Kace's unwavering conviction in the inevitable Mandalorian triumph, the Republic emerged victorious two years later when Revan defeated Mandalore and obliterated his forces by deploying the Mass Shadow Generator superweapon at the Battle of Malachor V.

By 3962 BBY, Dorjander Kace was a man of middle age, possessing fair skin, blue eyes, long, flowing blond hair, and a short, styled beard. Though a respected Jedi Master with a strong reputation, Kace was known to have been rebellious in his youth, which he acknowledged by describing himself as a former iconoclast. Neither this, nor his extensive time as a Mandalorian captive, prevented him from achieving the highest rank within the Jedi Order: membership on the Jedi Council. Kace was a gifted speaker, consistently drawing large audiences during his time on the Council, a skill he demonstrated repeatedly while addressing his Mandalorian troops and even during his own trial.
While living among the Mandalorians, Kace succumbed to his emotions and violated the Jedi Order's tenets of non-attachment by falling in love with Varda, whose bravery impressed him. They conceived a child. Varda shared her people's traditions with Kace, and he embraced the Mandalorian way of life. The death of Varda and their unborn child at the hands of a Jedi caused Kace deep emotional pain, yet he chose to return to the Jedi Order, though his beliefs began to shift from that point onward. When the Mandalorian Wars began, he openly opposed Revan's involvement in the conflict, a position initially supported by the majority of the Council. However, once the Council was compelled to endorse Revan's crusade, Kace's stance suddenly became problematic for the Republic, which required the Jedi's assistance in the war. Consequently, the Republic manipulated the situation to force Kace's resignation from the Council, another example of what Kace saw as the ingrained corruption that plagued the government and its unhealthy relationship with the Order.
Kace was utterly convinced that the Mandalorians were better equipped for the ongoing war and that, even with Revan's intervention, the Republic was destined to lose. However, he believed that such an outcome could benefit the galaxy, provided the Jedi Order guided the victorious Mandalorians. He initiated the integration of the Jedi into the Mandalorian ranks with himself and a small group of Jedi who embraced his teachings and became the first Mandalorian Knights. The Mandalorian Knights held Kace in high regard, believing that he had given their lives meaning. Conversely, the Mandalorian warriors under Kace's command were hesitant to accept Jedi as leaders, due to their distrust of the Force and those who could manipulate it. Kace was aware of this and sometimes feared that he was progressing too quickly with his plan. He strived to act in accordance with Mandalorian customs and demonstrate through his actions that the Mandalorian Knights were genuinely committed to the Mandalorian lifestyle. He respected their traditions and understood their warrior nature. While he accepted this to some extent, acknowledging that a war could not be won using only stun weapons and tolerating the unnecessary killing of the Bith on Phaedacomm, he hoped to moderate the Neo-Crusaders' violence with the aid of the Jedi Order.
Kace's plan to abduct the Jedi children was based on his belief in the Mandalorians' ability to convert those they conquered. However, he misunderstood that forced abduction was not part of their tradition. Nevertheless, Kace was determined to complete his mission, to the point that Zayne Carrick considered his obsession a sign of madness. He was even prepared to kill both Carrick and Koblus Sornell, and only the last-minute revelation of the Devaronian's pregnancy stopped him, as the Jedi Master realized that he was on the verge of committing the same act for which he despised the Republic. Although he surrendered, Kace maintained his convictions, labeling the current state of affairs, in which the corrupt Republic was so closely aligned with the Jedi Order, as "madness." He remained hopeful that the situation would change. Valuing family, Kace requested only that Sornell be allowed to return to her husband and son, stating that being with one's family was the ultimate purpose of the war.

As a fully trained Jedi Master, Dorjander Kace was skilled in both the Force and lightsaber combat. Although he neglected his lightsaber dueling skills for a considerable period after completing his Jedi training, he compensated by learning street-fighting techniques. He readily applied this knowledge in combat, as demonstrated when he kneed Zayne Carrick in the abdomen. He remained proficient with the lightsaber, employing it on numerous occasions—during the assault on Halthor, the skirmish on Phaedacomm, and the duels against Zhar Lestin and Carrick on Dantooine. Kace's lightsaber emitted a distinctive bronze color, matching the weapons of the other Mandalorian Knights. He possessed the ability of telekinesis, which he used to unmask Morvis on Dantooine. When the Bith technicians on Phaedacomm attempted to evacuate the station, Kace tried to use a mind trick to persuade them to stay, but he failed because Kra'ake opened fire on the Bith. During his Mandalorian Knight campaign, Kace donned a suit of gray Mandalorian armor equipped with a jetpack. He was also capable of piloting a speeder bike.
Dorjander Kace was conceived as the primary antagonist for Zayne Carrick in the 2012 Dark Horse Comics five-issue miniseries Star Wars: Knights of the Old Republic: War, penned by John Jackson Miller and illustrated by Andrea Mutti. The series was published from January 11th to May 9th. Kace appeared in all five issues of the series and was featured on the cover of the fifth issue, designed by Benjamin Carré.