A'den Skirata (with the pronunciation AH-den), initially designated as Null-12 and also called N-12, stood out as one of the six Null-class Advanced Recon Commandos who survived. Just like his Null ARC brothers, he received his name and training from the Mandalorian figure Kal Skirata.
Notably, A'den distinguished himself as the only Null ARC to attain the rank of sergeant, rather than becoming an officer. This decision stemmed from his deep respect for Skirata, who, in accordance with Mandalorian customs, formally adopted him and his fellow Nulls as his sons.
Commonly known as A'den, Null-12 originated as a clone derived from the genetic material of the Human male bounty hunter Jango Fett. As a member of the initial group of clones cultivated by the Kaminoan scientists, Null-12 came into existence in 32 BBY within the facilities of Tipoca City situated on the planet Kamino. Among the twelve clones comprising this initial batch, only six managed to survive the gestational phase: N-5, N-6, N-7, N-10, N-11, and N-12.
Upon reaching the age of two standard years, A'den, along with his five surviving brothers, underwent fundamental flash training administered by the Kaminoans. This educational process equipped the future ARC troopers—Advanced Recon Commandos—with fluency in Basic and provided instruction in essential war-related skills. Specifically, this military instruction encompassed the proper handling of various blaster weaponry and introduced them to simulated combat environments, complete with live explosive devices. These battle simulations instilled in A'den and the Nulls a childhood fear of thunderstorms, as the sounds of thunder and lightning closely resembled the explosions of bombs.
While A'den and his brothers demonstrated physical prowess, the Kaminoans' psychological evaluations revealed shortcomings in their conformity to established standards. Despite achieving exceptional scores on intelligence tests, they failed to align with the Kaminoans' desired personality profile. During training exercises, they exhibited traits of cunning and insubordination. These deficiencies—ultimately resulting from the cloners' deliberate genetic modifications aimed at enhancing Jango's template—led to the designation of the six boys as Null-class and their scheduled reconditioning.

In 30 B.B.Y., Kal Skirata, a member of Jango Fett's Cuy'val Dar, engaged in a meeting with Jango on Kamino, during which Orun Wa requested their assessment of the Null-ARCs and their professional insights. Skirata anticipated encountering fully grown men displaying subpar marksmanship, among other deficiencies, but was taken aback to discover that the six "defective" clones were merely four years old, having undergone two years of accelerated growth.
After Orun Wa explained that the boys were unmanageable and slated for termination due to their failure to meet stringent quality control standards, Skirata intervened immediately, vehemently opposing the Kaminoans' intention to eliminate the defenseless boys. Fett granted Skirata permission to escort A'den and the other Nulls to his quarters. It was within these confines that A'den experienced his first taste of sticky uj cake and received a proper name in lieu of his numerical designation.
Skirata swiftly assumed the role of a father figure to A'den and the Nulls, who affectionately addressed him as Kal'buir, meaning "Papa Kal." While preoccupied with instructing his other commando squads, he encouraged the Nulls to roam freely throughout Tipoca City. One of A'den's preferred pastimes during these excursions involved swinging from the ceiling using a rappel line and targeting Kaminoan technicians below, an act that invariably amused his brothers.
The Clone Wars commenced in 22 BBY, marked by the arrival of Master Yoda from the Jedi High Council on Kamino, who oversaw the deployment of all available troopers to Geonosis. There, the Jedi were engaged in the mission of rescuing Senator Padmé Amidala along with the two Jedi Obi-Wan Kenobi and Anakin Skywalker.
A'den and his brothers were dispatched to the front lines with such haste that they lacked the opportunity to awaken Skirata and bid him farewell.
Five days following the events on Geonosis, all six Nulls were scheduled for cryo-stasis in preparation for their next deployment. Overwhelmed by the prospect of facing cryo-stasis, the Nulls swiftly and efficiently shut down and barricaded themselves within the Special Operations barracks on Coruscant. Only the timely intervention of Skirata persuaded the Nulls to stand down, leading to his re-enlistment as a Sergeant in the Grand Army. Throughout the remainder of the war, they operated in black ops for the Grand Army of the Republic, ultimately reporting solely to Skirata.
In 21 BBY, A'den received orders to deploy to Gaftikar with the mission of assisting a reptilian species known as Marits in seizing control of the planet's major cities from the local Human population, who were receiving support from the Separatists. A'den's assignment entailed continuing the work initiated by Sull, an Alpha-Advanced Recon Commando who had mysteriously disappeared, by training the Marits in preparation for the impending invasion.
To provide support to the lone clone, clone commandos from Omega Squad were dispatched to deliver additional supplies, aid in the training of the Marits, and actively participate in the battle. A'den treated the squad members as his own brothers, even cautioning Atin Skirata, the squad's slicer, against inquiring about the ingredients of the Marits' stew. Despite the warning, the commando persisted in his inquiry and was horrified to discover that the reptilian species practiced cannibalism, consuming their own dead as a form of reverence.
Several days prior to the Marits' planned assault, A'den dispatched Darman Skirata and Atin on a reconnaissance mission to Gaftikar's capital city. During their scouting, the two commandos uncovered that Sull, the Alpha-ARC who had vanished, had in fact deserted and was now employed as a cab driver within the city. Darman and Atin reported their findings and apprehended the traitorous clone, transporting him to the resistance's camp for interrogation.
Initially, A'den permitted Omega Squad to be present during the interrogation but subsequently requested their departure to facilitate a private discussion with the fellow ARC. A'den ultimately released Sull, even arranging for his transportation off-world and the opportunity to vanish on Mandalore. Niner, Omega Squad's sergeant, vehemently opposed Sull's release.
The two Sergeants engaged in a heated verbal exchange, during which A'den became so incensed that he thrust his comlink into Niner's hand and challenged him to report the Alpha-ARC's actions to command. Ultimately, Niner was unable to comply and stormed off. With Niner out of earshot, A'den continued his impassioned speech regarding the clones' unjust circumstances to his commando brothers.
Shortly after Nyreen Vollen, a pilot A'den had encountered during previous undocumented adventures, transported Sull to Mandalore, A'den, the Marits, and Omega Squad prepared for battle. While Omega coordinated air strikes on the capital and A'den single-handedly deployed charges and jammers around strategic locations within the city, the Marits and a contingent of clone infantry initiated the ground assault. Their efforts culminated in the capture of the major cities and, consequently, the planet. The Marits achieved their original objective of proportional representation through their subsequent integration into the local Humans' political system.
Several days later, A'den journeyed to Coruscant to visit Fi, Omega's medic, who had sustained severe brain trauma during the battle on Gaftikar.
A'den eventually made his way back to Coruscant, where he was finally reunited with all five of his brothers and his father. Over a pleasant meal of nerf steaks, Skirata formally adopted A'den and the other Nulls as his sons, an act that filled A'den with immense joy. Their meal was interrupted by a Republic ensign, who criticized the lack of decorum in having a non-commissioned officer like Skirata in the officer's mess and behaved condescendingly toward the clone soldiers. Ordo engaged in a physical altercation with the ensign, compelling him to apologize to Sergeant Skirata, much to the Nulls' delight.
In the days leading up to Chancellor Palpatine's enactment of Order 66, A'den introduced Vollen to Skirata and became convinced that the two were well-suited for each other. He persistently attempted to arrange a romantic connection between Skirata and Vollen. He accompanied Vollen aboard her freighter to assist her in uncovering the circumstances surrounding her first husband's death, thus being off-world when Order 66 was issued.
A'den eventually reunited with his Null brothers, Skirata, half of Omega Squad, Walon Vau, Bardan Jusik, Atin's wife Laseema, Ordo's wife Besany Wennen, Besany's friend Jilka Zan Zentis, and Jango Fett's estranged sister Arla Fett at their homestead on Mandalore, formally deserting. After Skirata spoke with Vollen following their disembarkation with A'den, Yayax Squad, and the deceased Etain, it was revealed that Vollen had discovered the manner of her husband's death, with A'den's assistance. He was also present for the cremation of Darman's Jedi wife, Etain Tur-Mukan, who had perished while attempting to evade Order 66.
As Wad'e Tay'haai began playing the melody of Vode An on a Bes'bev, Mird joined in with howling along to the notes. A'den also joined in with the strill's howling, causing great distress to the creature, prompting raucus laughter from Vau.
During Order 66 on Coruscant, Darman and Niner of Omega Squad had been left behind. Skirata, with help from his Null sons, came up with a plan to rescue the two men. A'den initially expressed his desire to travel to Coruscant to assist with the extraction but was dissuaded by his brother, Ordo, due to his dark tan, which would make him conspicuous if they needed to blend in as regular clone troopers. A'den remained on Mandalore, assisting with the daily operations at the homestead.
A'den, along with several other clone deserters, was wanted by the Galactic Empire for his desertion. His Null brothers and him also tried repeatedly to set their father Kal up with the spacer Nyreen Vollen, though with little success. After is was discovered the Empire had Nyreen in their sights, Skirata, Ordo, Mereel, and A'den talked to her about her involvement with the Jedi. A'den was sympathetic towards Nyreen for being on a list of known Jedi sympathizers. He dedicated a significant amount of time post-war to devising strategies for rescuing their remaining brothers Darman and Niner, who had been stranded on Coruscant following the events at Shinarcan Bridge Extension/Shinarcan Bridge.
A'den exhibited both similarities and differences compared to his Null brothers. Like them, he bore the psychological scars of his flash training on Kamino and was prone to sudden outbursts. As a Null, he was also referred to as "death on legs" by his father and was occasionally perceived as eccentric by other clones. A'den harbored deep cynicism towards Palpatine and the Republic, expressing frustration at the latter's reluctance to strike at the heart of the Confederacy of Independent Systems. Similar to his Null brothers, he held a profound animosity towards the Kaminoans, particularly Ko Sai.
In contrast to his brothers, A'den possessed a naturally jovial disposition. He frequently joked and smiled, resulting in the formation of white lines around his mouth, indicating constant creasing of the skin. His lighthearted nature set him apart from his fellow Nulls, who tended to be more somber and melancholic. Despite his inherent cheerfulness, A'den was also capable of becoming enraged very quickly. This was evident during his dispute with Niner regarding the decision to release the ARC trooper Sull after he had gone AWOL. A'den was also the most talkative of all of his brothers and had no qualms about gossiping.
Shortly before the establishment of the Galactic Empire, A'den encountered and befriended Nyreen Vollen, who advocated for clones to possess the same rights and lifespans as ordinary beings. Nyreen, affectionately known as "Ny," would later assist the Skirata clan by transporting deserter clones to Mandalore to begin their new lives.
Kal Skirata served as A'den's adoptive father and the individual who saved the Null's life on numerous occasions. A'den and his brothers addressed Skirata as buir, meaning "papa," and exerted every effort to please him. Skirata aspired to grant his sons and every GAR clone a full lifespan, making it his life's mission. His unwavering affection for his sons engendered in them complete devotion and loyalty to him and his plans.
A'den shared a close bond with his fellow Null-ARC brothers—Ordo, Mereel, Kom'rk, Prudii, and Jaing. During their time on Kamino, A'den would often explore the Tipoca City complex with his brothers. They even engaged in pranks targeting the Kaminoan cloners, with A'den's stunt of shooting at the aliens eliciting much amusement among the Nulls. Throughout the Clone Wars, A'den was frequently separated from his brothers, but he always experienced the greatest happiness upon reuniting with his family.
As an Advanced Reconnaissance Commando, A'den received training akin to that of the Alpha-batch ARCs and utilized much of their equipment. He donned white plastoid composite armor adorned with green markings, signifying his rank as a sergeant in the GAR. Additionally, he wore a black kama and sported a rangefinder on his helmet. During the resistance on Gaftikar, A'den opted for plain civilian attire; however, he reverted to his customary armor as the time for battle drew near.
A'den Skirata was brought to life by Karen Traviss for the Republic Commando series. A'den made his debut in Republic Commando: Triple Zero, the second installment, and played a minor role in subsequent novels. A'den translates to "wrath" or "rage" in Mando'a. In The Complete Star Wars Encyclopedia, the entry for CT-80/88-3009, who shares the name A'den, mistakenly asserts that Null-12 and CT-80/88-3009 are the same individuals.