The Dyarchy's constituent territories consisted of the planet Byllura, a former Republic world that had been conquered by the Chagras Hegemony during the First Charge Matrica, a competition instituted by the Calimondra family matriarch Vilia Calimondra. Its capital city was Hestobyll, which was built as a river delta carved into a steep, diagonal slope at the interior of a large continent. While Chagras's youngest children Quillan and his sister Dromika were the nominal rulers of the Dyarchy, much of the Dyarchy's affairs were managed by their Krevaaki Regent and Sith Lord Saaj Calician. Calician used the twins' powerful Force bond to create a global telepathic transmission network that allowed the three Sith to directly control the daily functions and actions of their subjects. By 1032 BBY, Byllura's inhabitants had been reduced to the status of mindless drones whose sole existence was to serve their Sith overlords. Any visitors who visited the Dyarchy became ensnared and forcibly integrated into this telepathic network. This meant that very little reliable information about the Dyarchy escaped Byllura.
The Dyarchy's telepathic transmission network was transmitted by a network consisting of thousands of enslaved Celegians. These Celegians helped transmit messages and commands from the twins and Calician to the Dyarchhy's subjects. A force of red-clad Sith adepts known as the Unifiers functioned as the Dyarchy's primary law enforcement agency and were tasked with using Force persuasion to dull the minds of the Dyarchy's inhabitants and to send messages through the web. Under Calician's leadership, the Dyarchy also developed a significant military-industrial base for the purpose of launching a military expansion campaign against the Dyarchy's neighbors in the future. By 1037 BBY, the Dyarchy had also secretly constructed a fleet of fourteen battleships known as the Dyarchy Fleet beneath Hestobyll's reflecting pools. Each of these battleships was commanded by a single Celegian who answered directly to the Dyarchy's telepathic web. Due to its highly centralized nature, the Dyarchy's telepathic network was vulnerable to any direct attack on its core leadership. Following the capture of Quillan and the incapacitation of his sister Dromika, the network collapsed entirely which led to a mass uprising by its subjects.
Due to the collapse of much of the Grumani sector's hyperspace relays caused by the decline of the Republic, the Dyarchy had no reliable communication networks with offworld locations and remained isolated from its Sith neighbors and the Republic. The Dyarchy even lacked infrastructure for comlinks because Calician believed that a secondary communications system would provide a means for internal dissidents to coordinate resistance to the state. The Dyarchy's nearest neighbor was the Sith princedom known as the Daimanate, which was ruled by the late Sith Lord Xelian's younger son Daiman, who viewed himself as the Creator of the universe. Despite correspondences between Regent Calician and Daiman in 1037 BBY via hologram, the latter was unwilling to ally or engage in hostilities against the Dyarchy. Another known neighbor of the Dyarchy was another Sith state known as the Arkadianate, which was ruled by the twins' older sister Arkadia Calimondra. The Arkadianate was militarily stronger than the Dyarchy and posed a threat to the Dyarchy's existence by 1032 BBY. Unlike the Bactranate—another Sith state ruled by the Quermian Sith Lord Ayanos Bactra, the Dyarchy had no corporate assets.
The Dyarchy was formed following the death of the Sith warlord Chagras in 1040 BBY. Chagras was the sole surviving son of the Sith Lord and Calimondra family matriarch Vilia Calimondra and the sole winner of the Charge Matrica. Vilia had devised the Charge Matrica as a competition to select the most worthy heir to inherit her extensive holdings. She promised to grant her extensive assets and territories to the child who conquered the most territory. Chagras ultimately won this contest and became the ruler of a new Sith state known as the Chagras Hegemony. However, Vilia still lived and controlled much of her empire. His victory brought a brief period of stability to the Grumani sector and guaranteed Chagras the assistance of his nieces and nephews, so he tasked them with repairing the damage that the war had caused his holdings.
Around 1046 BBY, Chagras fathered two twins: a girl named Dromika and a boy named Quillan. When the twins turned five years old circa 1041 BBY, Chagras brought his children to live on Byllura under the care of Regent Saaj Calician. While the twins remained in an infantile state for much of their lives, Calician found that both of them had extraordinary Force abilities in certain areas that exceeded the powers of many other Sith. Quillan had a greater ability to predict the future than any other Sith that Calician had met, while Dromika was more proficient with the use of the Force to control the minds than anyone else he knew. Calician and the twins resided at The Loft, an exclusive private residence in Hestobyll, and never left its premises. They perceived the wider universe entirely through the Force and referred to all other sentient beings as "aspects." The twins regarded Calician himself to be their "regent-aspect," and he served as their main link to the outside world. He tended to their every need and he acquired some nanny droids, to care for twins when he wasn't present.
In 1040 BBY, Chagras died after being infected with a powerful nerve toxin. The Chagras Hegemony quickly disintegrated as rival Sith warlords fought each other and several new princedoms were formed. Without a heir to inherit her vast holdings, Vilia initiated a Second Charge Matrica among her grandchildren to select a new successor. Regent Calician took advantage of the crisis to establish the Dyarchy as a separate state and served as the mastermind behind the Sith twins. Putting his theories of a centralized Sith state into action, Calician established a global telepathic transmission network on Byllura. To do this, he lured and enslaved thousands of Celegians, a species of sentient invertebrates that resembled floating brains, and used their telepathic abilities to form a telepathic web. The result of Calician's experiment in thought control was the enthrallment of Byllura's people into mindless drones whose sole existence was to carry out the edicts of their Sith rulers.
Calician also created a de facto police force of Sith adepts known as the Unifiers to enforce compliance among the Dyarchy's subjects. The result of Callician's telepathic network was a highly centralized Sith state whose rulers directly imposed their will on their subjects. All visitors who visited Byllura were integrated into the Dyarchy's telepathic network which meant that there was little reliable information on the Dyarchy within the wider galaxy. By 1032 BBY, the mercenary leader Brigadier Jarrow Rusher had heard unconfirmed rumors that Byllura was under a Sith principality ruled by children and that it was managed from "behind the creche" by a regent. The Dyarchy's offworld contact was also limited by Byllura's remote location at the edge of the Grumani sector where there were few reliable hyperspace routes.
Over the next few years, the Dyarchy's population, manufacturing facilities and military capabilities expanded under Calician's guidance. However, as the twins matured, Quillan increasingly began to use his sister's Dromika's mental capabilities to take direct control of the Regent's mind. Sometimes, Calician found himself subsumed into the communications web that he had created, becoming an unthinking extension of the twins' will. In 1037 BBY, Calician also initiated construction of the Dyarchy Fleet, a force of battleships that was secretly constructed beneath Hestobyll's reflecting pools. Around this time, Calician also made contact with Daiman, the twins' cousin and the leader of the neighboring Daimanate Sith state, via hologram. While Calician had hoped to forge an alliance with Daiman, the self-proclaimed "Creator of the Universe" was unwilling to either ally with or engage in hostilities against the Dyarchy. By 1032 BBY, fourteen battleships in the Dyarchy Fleet were completed and Calician turned his attention to expanding the Dyarchy's territories, determined to export his own conception of the perfect "Sith state."
In 1032 BBY, a new threat to the Dyarchy came in the form of the lone Jedi Knight Kerra Holt. She was a Jedi operating "knight errant" missions in the Sith-dominated Grumani sector. Following the Battle of Gazzari, Kerra had escaped the planet on the mercenary leader Brigadier Jarrow Rusher's troopship Diligence with nearly 1,700 student passengers. Unable to travel to the Galactic Republic due to a lack of reliable hyperspace routes, Rusher took the Diligence to Byllura, the nearest known terrestrial planet in the sector. Since the students were placing a strain on the ship's space and resources, Rusher wanted to dump the refugees on the nearest habitable planet. Kerra and Rusher were unaware about the Dyarchy's existence and its Sith rulers. The Diligence landed at the spaceport in Hestobyll.
Concerned about the suitability of Dyarchy as a refuge for the students, Kerra convinced Rusher to allow her to do a one hour probe of the city. Kerra quickly discovered that the planet's inhabitants were mentally enthralled to a global telepathic network and found that the Celegians were serving as the transmitters within this network. For the Dyarchy's Regent, the arrival of the Diligence marked the first starship that had visited Byllura in years. Since the ship had previously originated from the Daimanate, Calician thought that Daiman's control over his domain had weakened. He ordered the Dyarchy Fleet to begin preparations for an invasion of the Daimanate's rearward systems. He also dispatched a party of Unifiers to impound the Diligence and "integrate" its crew. However, Rusher fought off the Unifiers and the Diligence managed to escape from its hangar bay after a skirmish.
Meanwhile, one of Kerra's charges the Sullustan student Tan Tengo left the ship to explore Hestobyll without Rusher's permission and the Brigadier sent one of his Troopers—the Duros recruit Beadle Lubboon to bring back the girl. Another party of Unifiers apprehended the pair and Kerra pursued them back to the Loft. After fighting her way through the palace, she encountered one of Calician's Celegians named "One" and convinced him to rebel against his Sith overlords by refusing to transmit any more commands across the telepathic network. "One" subsequently convinced his fellow Celegians to rebel and the Dyarchy's network broke down within hours. After dueling Calician and the twins in a heated skirmish, Kerra kidnapped Quillan. Her actions effectively decapitated the Dyarchy's command chain which further accelerated the collapse of the telepathic network.
The kidnapping of Quillan caused the breakdown of the Dyarchy's society and Byllura's inhabitants quickly regained control of their thoughts, actions, and behaviors after years of suppression. Riots quickly broke out in Byllura's population centers as the citizenry rebelled against the planet's Sith rulers. Meanwhile, Rusher rescued Tan, Beadle, and Kerra from the Loft, and took Quillan as a hostage. The Sith Lord quickly descended into an infantile tantrum while his sister Dromika fell into a coma. Free of the twins' control, Calician contacted Kerra and tried to convince her to kill Quillan in revenge for the mental enthrallment he had endured. Meanwhile, the Sith Lord Arkadia Calimondra invaded Byllura and her star fleet quickly wiped out the Dyarchy Fleet within minutes. She also trapped the Diligence in her warships' tractor beam projector and convinced Rusher and Kerra to follow her to Syned and offered to shelter the refugees.
With the Dyarchy's command structure destroyed, Arkadia's forces occupied Byllura with little resistance from the planet's population. The Bothan spy and independent operative Narsk Ka'hane was also present when Arkadia's soldiers executed Narsk, who accepted his end peacefully. Arkadia had ordered the execution of the Regent because she regarded him as the mastermind who had exploited her young siblings and a threat to her own ambitions. Arkadia promoted her Sith regime as a more enlightened regime and offered to integrate the Byllurans as Arkadianate citizens. Arkadinate forces also freed the Byllurans from their enslavement and took custody of both Quillan and Dromika. During a subsequent family Bequest, the family matriarch Vilia Calimondra formally recognized Arkadia's annexation of the Dyarchy.
Feigning to care for her brother, Arkadia also offered to send Quillan to Arkadia's secret retreat world which Vilia agreed. However, she planned to assassinate her grandmother and take advantage of the ensuing crisis to further her own territorial ambitions. She had prepared several warring parties for strikes on neighboring Sith states in the event her grandmother was killed. She also intended to kill Quillan by exposing him to the nerve toxin Chagras's Blood. Arkadia attempted to recruit Kerra but the Jedi Knight refused and the Sith Lord was forced to rely on the Bothan spy Narsk. However, Narsk was secretly working for Vilia and she ordered him to sabotage Arkadia's plans. He convinced Rusher and Kerra to stage a diversionary attack on Arkadia's capital of Calimondretta. Narsk then took advantage of the chaos to escape with Quillan to Vilia's secret retreat. The devastation on Calimondretta forced Arkadia to withdraw significant forces from Byllura and to suspend her plans of galactic domination.
The Dyarchy first appeared as a plot element in the second section of his stand-alone novel, Knight Errant, which was first released on January 22, 2011. Much of the information of that government from the novel is recorded from the point of view of Saaj Calician, one of the antagonists and the fourth major POV character.
- The Essential Reader's Companion