Sister Six was a Xexto assassin of the female persuasion, who became a member of Chelli Aphra's mercenary crew. Their mission was to retrieve Aphra's superior's memories, which led them to Skako Minor in search of Wat Tambor's workshop. However, an Imperial force led by Magna Tolvan ambushed them, inadvertently awakening a massive creature. After the beast was defeated, they plundered the workshop, and Aphra guided their departure.
Six, alongside the other mercenaries, then journeyed to a rebel flight academy. Initially mistaken as recruits, they were later apprehended by General Hera Syndulla upon revealing their true identities. Despite breaching their prison shields, they opted not to escape, which impressed Syndulla. When Syndulla inquired about their presence at the flight school, Sister Six stunned her, and subsequently, the other rebels present. The mercenaries proceeded to abduct Syndulla, intending to leverage her as a bargaining tool to gain access to Hivebase-1.
Aphra's scheme to penetrate Hivebase-1 proved successful in terms of initial entry without detection. They then engaged in conversation within a chamber housing discarded prototypes, and after inadvertently communicating with Tolvan, Aphra's presence was exposed to the Imperials. The prototypes were activated from their frozen state, prompting Six and the others to seek cover. Aphra strategically utilized Caysin Bog as a diversion so Tam Posla would combat the prototypes on their behalf. Subsequently, Six accompanied Aphra and Syndulla to the Hivebase-1 datacore. Despite encountering further Imperial resistance, Aphra skillfully employed her bugs to extract the datacore from Hivebase-1.
Following these events, Aphra, Six, Posla, and Syndulla made their way back to the flight school, where Syndulla commended them for the datacore heist. Six opted to remain with the rebels, while Aphra departed with Posla.
Sister Six once belonged to the Central Isopter, a cult that revered death and resided in violent regions like Jedha, before her expulsion due to laughter during sacred recitations.
Around 1 ABY, Six, working as an assassin, became part of a mercenary crew led by the archaeologist and Doctor Chelli Aphra, on Son-tuul. The team also included: Rexa Go; Hallio Bas, their Skakoan guide; Tam Posla, a former lawman from Milvayne; Caysin Bog, a cyborg and Posla's romantic partner; Glahst Ombra, a passive aggressive Defel; The Violet Ghost, a stranger known for his sword skills; and Dek-Nil, a reprogrammed first generation droideka.
The team's mission was to recover the memories of Aphra's superior, a figure unknown to most of the crew, except for Rexa. However, before they could leave Son-tuul, Aphra was instructed to abandon one of the mercenaries. She chose the Violet Ghost, who was deceived into defending against approaching stormtroopers while the others escaped the Son-tuul Spaceport.
Six and the team's initial destination was Skako Minor, specifically Wat Tambor's workshop. Guided by Bas, the group journeyed across the terrain to reach the workshop. However, Bas led them directly into a squad of stormtroopers, blocking the entrance. Bas revealed his betrayal and demanded the Imperials leave Skako Minor, as promised. The Imperial officer refused, but Aphra gave Bas her Tooka Flufto. Unbeknownst to Bas, Tooka was bio-engineered to explode upon hearing Aphra's code-phrase, which she recited, resulting in Bas and the Imperials being consumed in an explosion.
Following the explosion, Aphra had Rexa open the crate she had been carrying. Six assumed it was alcohol, but instead, it contained sixty more shrink-frozen Tookas, all similarly bio-engineered. Six then noticed a running stormtrooper, and Rexa ordered them to stop it. As the trooper passed Posla and Bog, they refused to intervene, citing that he had not broken any law. However, Ombra killed the stormtrooper as it entered the treeline.
Inside the workshop, the mercenaries found themselves in a room filled with machines and artifacts. As they examined the objects, a Delta-class T-3c shuttle crashed through the roof, carrying a squad of stormtroopers led by Lieutenant-Inspector Magna Tolvan. Unfortunately for both sides, the commotion awakened the Chthonic worm god, a large beast in the center of the room. It attacked, killing stormtroopers and forcing the rest of the combatants to take cover. Aphra attempted to assist with her Tooka, but the beast trapped her and Tolvan in a confined space.
While the beast was distracted, Ombra abandoned the group, and Six suggested they help Aphra. Posla objected, arguing that the monster had not broken any law. However, Six pointed out that Bog was lying lifeless behind them. Enraged by his soulmate's apparent demise, Posla activated his cybernetic missile launchers and fired at the monster. Bog then revived, calming Posla, who embraced him. Dek-Nil then fired a shot that caused a stormtrooper to fire their rocket launcher at the ceiling, causing rubble to fall onto the beast, killing it. Aphra declared victory and congratulated the others, urging them to continue looting. While Six and the others did so, Rexa investigated Aphra's activities behind the rubble. The others heard a gunshot, but Aphra reappeared and told them to keep looting.
As they returned to their gunship, Six found Ombra rejoining them. They departed Skako Minor, and Aphra reviewed the recovered data, concluding that her superior's memories were stored in Hivebase-1, the R&D center of the Tarkin Initiative.
Aphra's plan to infiltrate Hivebase-1 involved traveling to the Lucrehulk Prime, a Lucrehulk-class LH-3210 cargo freighter used as a flight school for the Rebel Alliance. The Alliance officer Bini mistook them for recruits and led them to General Hera Syndulla. During their walk, Six inquired about Ombra's whereabouts, and Aphra replied that she had left again after they landed. As they approached the control core, the Tooka Aphra was holding was drawn to it and ran inside. Aphra followed, but Syndulla shot the Tooka. Bini introduced the group, still believing they were recruits. However, Posla revealed their true identities, and Syndulla realized they were mercenaries. As the rebels aimed their weapons, Aphra asked Six about their chances of taking them on and reaching their ship in time. Six stated it was possible, but with sacrifices, so Aphra had them surrender.
The mercenaries were imprisoned in the brig, behind energy shields. While Six sat with Posla and Bog, they heard a commotion in Aphra's cell. Ombra had entered through the vent. Aphra realized it was Magna Tolvan disguised as the Defel, and Tolvan aimed a blaster at her. Dek-Nil, who was on the other side of Aphra's cell, stunned Tolvan, who accidentally shot the shield generator, deactivating the energy shields. The mercenaries were now free, and Aphra instructed them to help her stuff Tolvan back into the vents.
When the rebels found Six and the others, they were still at their cells. Syndulla respected this and decided to listen to why they were at the flight school. Posla was about to explain his plan to get into Hivebase-1 when Bog opened his neck compartment, revealing four blasters. Six caught them and quickly stunned Syndulla, Bini, and every other rebel in the hanger. As the mercenaries carried Syndulla to their ship, Posla was furious that he was unaware of their plan. Bog tried to calm him, but he threatened to quit. Aphra was about to leave him to the reinforcements when he changed his mind and boarded the ship.
As they departed the Lucehulk Prime, Aphra borrowed a transmitter and contacted Hivebase-1, offering to trade Syndulla. Later, Aphra was running diagnostics on Bog when she asked Posla about the cyberneticist he was obsessed with. Together, Bog and Posla told her about Doctor Cornelius Evazan and Posla's pursuit of him. Six called him obsessive, but Bog corrected it as attached. As they finished explaining their intentions, their ship approached Hivebase-1. The officer confirmed their deal and provided a flight path. Aphra, however, was using Syndulla's general plaque, which had a tracker, to lure in the Lucrehulk Prime. With the rebels' arrival, Aphra used the chaos to sneak their ship into one of Hivebase-1's hangers.
The mercenaries left their ship and began snooping around. They entered a room of frozen prototypes that had been rejected before mass production. Fearing they might suddenly defrost, Six suggested giving Syndulla a gun, but Aphra refused. As they looked around, Aphra tapped into the Lucrehulk Prime's comm channel and discovered that Tolvan had commandeered the control core. Aphra contacted her and convinced her not to destroy the ship, but at the cost of revealing their presence in Hivebase-1.
Commander Yewl of Hivebase-1 ordered the prototypes to be defrosted, and the mercenaries found themselves surrounded by the rejects. They immediately attacked, gunning down Dek-Nil, and Syndulla demanded a gun from Six. Aphra stopped her, saying Syndulla would shoot them the second she had a chance. Thus, Six continued shooting at the prototypes until Aphra ordered the group to return to the ship. Bog, however, ran towards the rejects, being shredded by blaster fire. Posla watched his partner die and, in a fit of rage, revealed his cybernetic weapons and faced off with the prototypes. Six felt sorry for him, but Aphra pulled her away, and they left the room, leaving Posla to fight the rejects alone.
Aphra led Six and Syndulla to the Hivebase-1 datacore, where she began searching for her superior's memories. Syndulla asked Six again for a blaster, warning that Imperial reinforcements could arrive at any time. Posla then caught up with them, mourning Bog's death. As Syndulla and Aphra argued, the latter let Six give Syndulla a gun. Syndulla then tried to shoot Aphra when Commander Yewl arrived and intervened, zapping Syndulla. He ordered his forces to capture her and kill the others.
Yewl's forces engaged the mercenaries, but only Six fired back. Posla was still traumatized from his partner's death, and Syndulla was using Aphra as a shield. Aphra picked up Syndulla's blaster and gave it back to her so she could cover her. Aphra then used her AJ^3 cyborg construct and the terminal to connect with a bug she had planted in the Lucrehulk Prime's control core during her visit there. She had the flight school latch onto Hivebase-1 and rip the datacore—with Aphra, Six, Syndulla, and Posla inside—out with its tractor beam and X-wing starfighters.
Simultaneously, the sixty shrink-frozen explosive Tookas escaped their crate and left Aphra's ship to roam the rest of Hivebase-1. To help with this, Aphra sliced the firing registry and renamed it with the code phrase that detonated the Tookas. When the complex attempted to fire on the Lucrehulk Prime, it was destroyed by the dozens of Tooka's detonating.
With the datacore now in rebel hands, Syndulla complemented Aphra and the other mercenaries' efforts but politely asked them to leave. Six, however, decided to stay with the rebels instead. She had been impressed by them and desired to fight with people who believed in something. Aphra called it a happy ending and departed with Posla. In reality, Posla was Tolvan in disguise, the real Posla having been left gagged in the vents.
Tolvan eventually joined the Alliance and formed the unit Strike Team Misericorde, with Six joining as a sergeant. Around 2 ABY, the strike team was sent to Unox to apprehend the thief of the ancient lightsaber sniper rifle hybrid known as the Farkiller. Riding on a speeder bike, Six found that the thief was Aphra, becoming worried as Tolvan was convinced she had killed Aphra.
Sister Six was a female Xexto who possessed green skin, white eyes, and red hair. Her fascination with death led her to the Central Isopter death cult, and she found stun blasters unsatisfying because they did not result in fatalities. Despite her past association with death worship, Six considered herself more sane than her mercenary colleagues on Skako Minor. She was also highly observant of her surroundings, frequently considering possible scenarios. Despite her work as an assassin and mercenary, Six eventually realized she needed to fight for something she believed in and joined the Alliance.
Sister Six wore a brown hat and a white shirt with a sand-colored vest and mud green shorts. Her lower left arm was robotic, and she possessed several blasters, including an NN-14 blaster pistol, a stockless EE-3 carbine rifle, and two unidentified blaster pistol models.
Sister Six made her debut in the canon comic Doctor Aphra (2016) 15, penned by Simon Spurrier and illustrated by Emilio Laiso.