During the twilight years of the Old Republic, a Falleen female named Zule Xiss served as a Jedi Padawan. Known for her aggressive and impetuous nature, she became the apprentice of Glaive, a Human Jedi Master, before the Clone Wars erupted. A few weeks following the Battle of Geonosis, Zule and her Master, along with Jedi Obi-Wan Kenobi and Anakin Skywalker, were sent to the Naboo system in response to communications breakdown with the Gungan settlement on Naboo's moon, Ohma-D'un. Upon their arrival, the Jedi and their accompanying clone troopers discovered the Gungans dead, victims of an experimental swamp gas biological weapon deployed by the Confederacy of Independent Systems. Before Zule and the Republic forces could relay a warning about the gas to Naboo, they were ambushed by Durge and Asajj Ventress, agents of the Confederacy. In the resulting skirmish, Ventress brought about Glaive's demise and severed Zule's arm. Xiss, alongside Kenobi, Skywalker, and Advanced Recon Commando Alpha-17, managed to flee Ohma-D'un.
Now without a Master, Xiss became a member of the "Padawan Pack," a group composed of Jedi apprentices who had lost their Masters during the war. One year after the Ohma-D'un genocide, the Padawan Pack was deployed to the war-torn world of Jabiim to fight for the Republic. Command of the Republic army on Jabiim was delegated to Xiss and her fellow orphaned Padawans, as all Jedi of higher rank had fallen to the Jabiimi Nationalists, a pro-Confederacy faction seeking Jabiim's secession from the Republic. After weeks of combat, the Padawan Pack retreated to Cobalt Station, only to be attacked by the army of Alto Stratus, the leader of the Jabiimi Nationalists. The battle at Cobalt Station stretched for several days, during which Xiss began a descent toward the dark side of the Force, growing increasingly ruthless on the battlefield. On the forty-first day of the Battle of Jabiim, Zule Xiss met her end when she was crushed by a damaged Republic AT-AT while engaging enemy forces. By the battle's conclusion, every member of the Pack, with the exception of Anakin Skywalker, had perished, and the Republic was forced to abandon the planet days later. The surviving Republic forces retreated to New Holstice, where Skywalker added Xiss's name to a memorial honoring fallen Jedi.
Zule Xiss, a female Falleen, was a member of the Jedi Order serving the Galactic Republic during the Clone Wars. Her fiery temper and stubbornness made her a challenging student, resulting in her transfer between several Jedi Masters during her time as a Jedi Padawan. Her rebellious nature even prompted the Jedi High Council to foresee her eventual death in a bar brawl. Ultimately, she became apprenticed to Glaive, a Human Jedi Master known for his own abrasive personality. During her training with Glaive, she became acquainted with Vaabesh, a fellow Padawan of the Gand species. Vaabesh admired Glaive's mentorship of Xiss, but the Falleen would later express her disdain for her Master. Following the Battle of Geonosis and the commencement of the Clone Wars, Xiss and Glaive joined the Grand Army of the Republic in their fight against the Confederacy of Independent Systems.
Ten weeks into the war, Boss Rugor Nass, the leader of the Gungan, lost contact with a Gungan colony on Ohma-D'un, a moon orbiting their homeworld of Naboo. Queen Jamillia of Naboo, suspecting disgruntled spice miners were responsible, contacted the Jedi Order to request an investigation. The Jedi Council, however, believed a Confederate attack was the cause and dispatched Zule Xiss, Glaive, Obi-Wan Kenobi, and his apprentice, Anakin Skywalker, to the moon. The four Jedi, accompanied by a contingent of clone troopers and the Advanced Recon Commando Alpha-17, traveled to the Naboo system. Upon reaching the system, C-3PO, a protocol droid serving Queen Jamillia, briefed Xiss and her companions on the situation. The Jedi, Alpha, and several clones then descended to Ohma-D'un's surface in a single LAAT/i gunship to search for the Gungans.

Xiss and the Republic forces soon stumbled upon a horrifying scene: the massacre of the entire Gungan colony. The Jedi engaged several Confederate battle droids examining the bodies, concluding that spice miners were not responsible. The true perpetrator, Durge, the Gen'Dai bounty hunter employed by the Confederacy, revealed himself and confronted the Republic forces. During the ensuing melee, Xiss managed to stab Durge in the abdomen; however, his Gen'Dai physiology allowed him to withstand the injury. Durge retaliated by striking Xiss across the face, knocking her unconscious while Glaive engaged the bounty hunter. Overwhelmed, Durge called for reinforcements in the form of super battle droids carrying the swamp gas responsible for the Gungan deaths. While Kenobi and Glaive struggled with the gas and Skywalker and Alpha searched for hostages taken by Durge, the Gen'Dai found Xiss's unconscious body and lifted it. Glaive attempted to use a mind trick to force Durge to release her, but Kenobi intervened, attacking Durge from behind. Shortly after, Glaive was killed in a surprise attack by Asajj Ventress, the Dark Acolyte, Durge's ally and the Separatist commander responsible for the Gungan genocide.
Durge and Ventress nearly killed Kenobi, but Xiss, having regained consciousness, saved him by driving her lightsaber into Durge's back. However, Durge's lack of a central nervous system allowed him to continue fighting, tackling Xiss as he explained this. He smothered the young Falleen and began cutting her face with a large blade, but before Durge could kill her, Xiss grabbed the blasters from his holsters and shot him in the chest. Rejoining Kenobi, she watched Durge leave to hunt down Alpha and Skywalker while Ventress stayed to finish off Kenobi and Xiss. Using the dark side, Ventress reanimated many of the dead Gungans to overwhelm the two Jedi. Xiss recovered her lightsaber, but before she could attack Ventress, the Dark Acolyte cleaved off her left arm. Weakened by the poison gas and wounded by Ventress, Xiss was nearly killed before Skywalker and Alpha returned to aid her and Kenobi. Outnumbered, Ventress and Durge abandoned their mission and fled Ohma-D'un. Xiss accompanied Alpha as he carried Glaive's body onto their LAAT/i alongside Kenobi and Skywalker. The group then left the moon to warn the Jedi Order about the new swamp gas weapon threat.

Following the Ohma-D'un genocide, Xiss received a cybernetic arm to replace the one Ventress had severed. She subsequently joined a group of Padawans who had also lost their Masters during the war. This group, known as the "Padawan Pack," included Xiss, Windo "Warble" Nend, an Aqualish, Elora Sund, a Sullustan, Kass Tod, a Zabrak, Tae Diath and Mak Lotor, both Humans, and Vaabesh, Xiss's old acquaintance. The Padawan Pack was assigned to the war-torn world of Jabiim, where political unrest had sparked a civil war. Jabiim, a Republic world largely ignored by Coruscant, was left to grapple with its problems without the Jedi or the Republic's Judicial Forces. Alto Stratus, a prominent Jabiimi politician and leader of the Nationalist party, advocated for Jabiim's secession to the Confederacy and, after forming an alliance with Count Dooku, the Confederacy's Head of State, killed most of the pro-Republic members of the Jabiim Congress. However, before Stratus could use the Confederate droids and arms provided by Dooku to eliminate pro-Republic forces, the Grand Army of the Republic invaded the planet to support Captain Orliss Gillmunn and his Jabiimi Loyalists in their fight against Stratus and the Nationalists.
Xiss once again fought alongside Alpha-17, Anakin Skywalker, and Obi-Wan Kenobi, who had been appointed theater commander for the Jabiim conflict. By the thirtieth day of battle, eighteen Jedi and nine thousand clones had perished. Kenobi and Jedi General Sirrus were presumed dead, adding Skywalker and Sirrus's apprentice, Aubrie Wyn, to the Padawan Pack. General Leska, now the highest-ranking Jedi on Jabiim, ordered the Padawan Pack to avoid the front lines and protect a supply convoy headed toward Cobalt Station, refusing to send more Padawans to their deaths. While guarding a convoy of All Terrain Experimental Transports and All Terrain Tactical Enforcers, the Padawans were attacked by Stratus's droid forces. Xiss followed Skywalker and several other members of the Pack into battle against the droids while Wyn and Nend remained with the convoy. Knowing the battle droids were single-minded, the Padawans distracted them with an obvious target before launching a successful ambush. This tactic, developed by Skywalker and his Master, repelled the droids and allowed the convoy to proceed. Despite the victory, Xiss remained pessimistic, noting that even the most advanced Padawan, Mak Lotor, was inexperienced in war. Later, Windo Nend attempted to engage Xiss in conversation, but she quickly became annoyed and threatened the Aqualish. Vaabesh explained to Nend that she was only defensive due to the loss of her Master on Ohma-Du'n, whom Vaabesh believed had truly taught Xiss what it meant to be a Jedi.
On day thirty-four of the battle, the convoy protected by the Padawan Pack drove directly into a minefield set up by Alto Stratus's Nimbus commandos. Unable to safely navigate the field, the trapped convoy was quickly attacked by Stratus's forces. Although Kass Tod ordered the convoy to remain stationary to avoid the mines, Xiss and Skywalker insisted on fighting back. After Mak Lotor passed out from overexerting himself in the Force while remotely detonating several mines, Xiss helped him move to cover. The Jabiimi Nationalists soon retreated, allowing the convoy to continue to Cobalt Station. There, while enjoying a brief break in the rain, Xiss and the Padawans witnessed Confederate reinforcements landing on the planet. During a communication with Orliss Gillmunn, the Padawans learned that General Leska had gone missing and that they were now the highest-ranking members of the Grand Army of the Republic on Jabiim. Cobalt Station was the last remaining Republic fortification on the planet, standing between Stratus's approaching forces and Monsoon Mesa, the evacuation site for the remaining Jabiimi Loyalists and clone troopers.

Despite the likelihood of defeat, all of the Padawans agreed to remain at Cobalt Station to buy time for the escaping Republic forces. Initially hesitant, Xiss ultimately decided to stay and fight, finding solace in the thought that her death would occur on the battlefield rather than in a cantina brawl. While preparing for Stratus's assault, she armed herself with a DC-15S. When the Confederates attacked, they found Cobalt Station's defenses far stronger than anticipated. Xiss spent time in the station's trenches with Windo Nend, encouraging her allies to push their attacks. On the second day of the assault, Xiss moved about the battlefront, using both a blaster rifle and her lightsaber to attack her enemies. By this point, her aggression worried her fellow Padawans, with Mak Lotor suggesting she was falling to the dark side.
Embracing the anger her Masters had warned against, Xiss killed many members of the Nimbus Commandos. Fighting in the shadow of one of the Republic's few remaining AT-AT walkers, Xiss maimed a Nimbus commando and prepared to execute him. However, before she could, the AT-AT was struck by heavy fire and collapsed, crushing both Xiss and the commando.

The Battle of Jabiim concluded two days later with Aubrie Wyn killing Alto Stratus. Despite Stratus's death, all Republic forces at Cobalt Station perished, including the remaining members of the Padawan Pack. Anakin Skywalker, recalled from the battlefront days earlier, arrived at Monsoon Mesa to oversee the evacuation of surviving Republic forces. Ignoring the pleas of the Jabiimi Loyalists seeking to flee their home and the Nationalists' reprisals, Skywalker chose to evacuate only the Republic's clone troopers due to transport limitations. Despite the Padawans' efforts to protect them, Skywalker and the clone forces, having earned the hatred of Orliss Gilmunn and the Jambiimi, departed the planet for the Republic hospital world of New Holstice.
On New Holstice, Skywalker was shown a monument for fallen Jedi built by the planet's natives. Skywalker added the names of his fallen comrades, including Zule Xiss, to the monument, whispering their names into memory moths, whose wings would eternally whisper the names. Supreme Chancellor Palpatine's administration later covered up the struggles and failure of Xiss and the Padawan Pack on Jabiim to prevent negative warfront news from reaching the public.
Zule Xiss was an abrasive Padawan, prone to anger and often demeaning to others. Her attitude problems led to her transfer between Masters until she was placed under Glaive, who was similarly abrasive and served as her final Master until the Ohma-Du'n mission. During the mission briefing, Xiss expressed skepticism about the Gungans' combat abilities, claiming they would be no match for vengeful spice miners. She also held a low opinion of clone troopers, surprised when Alpha-17 rebuked her, believing clones lacked independent thought. After Ventress killed Glaive, Xiss vowed to fight in his honor, declaring that she and Kenobi would kill Durge and the Dark Jedi for her Master's sake.
However, Xiss's reverence for her late Master quickly faded after Ohma-Du'n. She grew colder and less tolerant, becoming completely distanced from her peers by the time of her Jabiim tour. She refused conversation and held a pessimistic view of the Padawan Pack's abilities. When Windo Nend tried to interact with Xiss, he was met with threats and irritation. While Vaabesh attempted to rationalize her anger by attributing it to her difficult apprenticeship and the loss of her Master, Xiss denied Glaive's influence, claiming she hated him and wished she had killed him herself.
When deciding whether to abandon Cobalt Station or fight to the death, Xiss was the only Padawan hesitant to stay. She eventually relented, finding comfort in dying on the battlefield rather than in a cantina brawl. As the battle continued, the jaded Xiss slid toward the dark side, embracing her aggressive nature and using it to her advantage against Confederate forces. At least one Nimbus Commando referred to her as a monster after witnessing her brutality. Despite her resentment of both allies and enemies, Xiss wished her comrades well in her final moments.
Xiss's behavior deviated from most members of her species, openly displaying raw emotions and maintaining a constant shade of red in her skin pigmentation. She typically wore sleeveless robes and carried a green-bladed lightsaber.

As a Jedi Padawan, Xiss was trained in lightsaber combat and Force usage. On Ohma-Du'n, she dueled both Ventress and Durge, landing surprise blows on the latter—an impressive feat given Durge's Gen'Dai physiology and skill. She was less successful against Ventress, who severed her arm before they even fully engaged. Despite the beating from Durge, the amputation by Ventress, and the effects of the swamp gas, Xiss remained determined to survive, picking up her lightsaber and joining Kenobi, Skywalker, and Alpha in their advance on Ventress.
On Jabiim, Xiss fought for days with little rest in harsh conditions. Though trained only in lightsaber combat, she took up a blaster rifle while defending Cobalt Station. As she slipped toward the dark side, Xiss used her hatred and anger to fuel her aggression on the battlefield. In her final battle, she wielded her lightsaber once more, inspiring fear in her enemies with her brutality.
Zule Xiss debuted in Republic 51 within The New Face of War, a story arc of the Star Wars: Republic comic book series. She later returned in The Battle of Jabiim story arc, which depicted her death. Xiss also received an entry in the 2008 The Complete Star Wars Encyclopedia.
The script of The New Face of War identifies Xiss as a Falleen, despite her appearance suggesting otherwise. She lacks many common Falleen characteristics, including green skin, scales, clawed hands and feet, and prominent facial and spinal ridges. While her red skin color could be attributed to the Falleen ability to alter skin pigmentation, some have suggested she is a Zeltron due to her closer resemblance. When questioned, Lucasfilm official Leland Chee confirmed that Xiss was indeed a Falleen.