The Grysk Hegemony constituted a dominant power established by the warlike Grysk species. Their territory was situated within the uncharted expanses of the Unknown Regions in the galaxy. They were generally perceived as nomadic, and their existence was often relegated to the realm of semi-legend, even among inhabitants of the Unknown Regions. The Grysk employed "client species," one example being the Agbui, and possessed the capability to manipulate the minds of subjugated populations, compelling them to willingly serve and even die for their Grysk overlords. Consequently, a small number of Grysks could effectively control entire planets. During the reign of the Galactic Empire, the Grysk Hegemony initiated advancements into Imperial territories located in the Outer Rim.
The Grysks founded and governed the Grysk Hegemony, an empire situated in the Unknown Regions of the galaxy. Their empire established the Grysk military and engaged in conflict with various entities, including the Chiss Ascendancy and other species, conducting a series of conquests across the region. The Chiss Ascendancy sometimes opted to merely observe battles rather than actively participate. Following these conquests, survivors created memorial artworks, while Grysk warriors deliberately damaged the right sides of their helmets and armor.
As the Clone Wars unfolded in the better-known regions of the galaxy between the Galactic Republic and the Confederacy of Independent Systems, the Grysk Hegemony initiated surveillance operations targeting both the galactic government and the secessionist movement to gather intelligence. Concurrently, the Grysks were actively plotting to overthrow the Chiss Ascendancy in the Unknown Regions. By manipulating General Yiv and his Nikardun Destiny as puppets, the Grysk figure known as "Jixtus" orchestrated Yiv's aggression against the Chiss during the Nikardun conquests.
Seeking to gain control over the Confederacy, the Hegemony provided Head of State Count Dooku with information regarding cortosis, a material that offered effective protection against blasters and lightsabers. Subsequently, the Confederacy established a factory on Mokivj to produce B2-series super battle droids equipped with cortosis armor. However, the factory also began producing clone trooper armor under the direction of the Sith Lord Darth Sidious in preparation for the impending Order 66. The Chiss Mitth'raw'nuruodo, known as "Thrawn," later inferred that the Grysks had intended to withhold the full potential of cortosis from Dooku until he aligned with their objectives, but the production of clone armor surprised the Grysks. This surprise, coupled with a reassessment of their plans, led them to postpone their advance into the galaxy.
Ultimately, the cortosis factory was shut down through the combined efforts of Thrawn, then a Senior Captain in the Chiss Expansionary Defense Fleet investigating the Nikardun threat, and two Republic operatives: Jedi General Anakin Skywalker and Senator Padmé Amidala. Thrawn's acquisition of a Separatist deflector shield generator during his mission with Skywalker and Amidala aided him in suppressing Yiv's conquests during the battle over Primea. Nevertheless, he suspected that the general was serving a hidden master or that another force would emerge after the Nikardun.
Jixtus initiated a new plan to conquer the Chiss. Initially, Jixtus's Agbui clients, led by Haplif, attempted to incite a Chiss civil war, but Thrawn and his allies thwarted this effort in 18 BBY. Subsequently, Jixtus, with the assistance of the Kilji Illumine, a theocratic government under Grysk control, executed the Grysk plot to engineer a Chiss civil war. Despite Thrawn and his allies ultimately prevailing, with Jixtus himself meeting his demise in the Sunrise confrontation, Jixtus vowed that the Grysks would return. Recognizing the threat to his people and the imminent possibility of civil war, Thrawn orchestrated his own exile into the broader galaxy following his actions at Sunrise. He sought to engage with the newly established Galactic Empire, either to secure assistance in the battle against the Grysk or to weaken the Empire into a more attractive target.
Even with Thrawn's departure, the threat of civil war persisted. By 2 BBY, it was plausible that one Chiss faction had already fallen under Grysk influence. Meanwhile, Thrawn found himself in a more advantageous position than anticipated, receiving an offer to join the Imperial Military. This led to his extended service within Imperial space, where he ascended through the ranks alongside his protégé, Eli N. Vanto. Thrawn eventually attained the military rank of Grand Admiral. Despite his allegiance to the Empire, Thrawn dispatched Vanto to the Chiss to integrate into their ranks.
After suspending their operations during the Clone Wars, the Grysk finally returned to the galaxy proper, launching an expedition to the Outer Rim and initiating the colonization of moons orbiting the planet Mokivj. These actions prompted the Galactic Empire to push back the Grysk forces. In the aftermath of the campaign, Thrawn informed Sith Lord Darth Vader—the Sith identity of Anakin Skywalker—that he believed the Grysk were planning an imminent invasion of the known galaxy. He also acknowledged the potential for Grysk influence within the Chiss Ascendancy, noting the possibility of a brewing civil war among his people. Indeed, the Grysk had uncovered the secret of Chiss hyperspace navigation, the Sky-walker corps. Nevertheless, bound by his promise to Galactic Emperor Sheev Palpatine, a promise enforced by Vader, Thrawn was obligated to prioritize the Empire's interests over those of the Chiss during his service in the Imperial Military. Thrawn used his full Chiss name while addressing the Grysk force, hoping to deceive them into attacking his own people before the Empire, believing that the Grysk would maintain their tendency to attack the nearest enemy first.
The Grysk soon resurfaced and began encroaching upon Imperial territory, committing various criminal acts as noted by Chiss Admiral Ar'alani. One such incident occurred at the wreckage of the Allanar N3 light freighter, where an armed Grysk warship lay hidden, awaiting an opportunity to ambush the Empire. The Chiss intervened to divert the Grysk warship's laser fire. Upon the Grysk's retreat, the Empire captured two Grysk prisoners. Furthermore, upon examining the conjoined Grysk warships, the Imperials discovered nitrogen cylinders intended to destroy all evidence within four hours. However, the Empire managed to detach the Grysk ships from the triad poles before the nitrogen bombs could detonate. This did not prevent another Grysk attack, as two more Grysk warships emerged from hyperspace. The Chiss, prepared for their arrival, confronted them, demanding that the Grysk Hegemony withdraw from Imperial-controlled space. The Grysk commander sarcastically inquired whether the Chiss were serving the Empire and dismissed recent Grysk defeats, including the loss of two warships, as insignificant.
As the Grysk starfighters approached, the Chiss crew deployed plasma spheres, which disabled their missiles and caused them to explode. The surviving starfighters returned to their warships to inform newer reinforcements about their enemy's defenses. Following the defeat of the Grysk forces that entered Imperial space, Thrawn had another meeting with Palpatine, where he reiterated that the Grysk posed a threat to both his people and the Empire. He requested the authority to combat them, arguing that they threatened the regime he had pledged to serve. Contemplating Thrawn's claim, Palpatine privately concluded that the most effective way to defeat the Grysk would be to compel Thrawn to betray the Chiss and bring the Ascendancy under his control.
The Grysk Hegemony possessed a military that played a crucial role in the conquests within the Unknown Regions. This later resulted in a conflict with the Galactic Empire.
Rumors circulated that their forces attacked with overwhelming numbers. Grysk warriors served as the military's ground troops, utilizing lighting guns and pellet guns.
The Grysk Hegemony was an adversary of the Chiss Ascendancy, as well as other organizations and species. However, the Hegemony maintained active alliances with other factions. The Hegemony also collaborated with the Confederacy of Independent Systems by providing crucial information in an attempt to weaken the Galactic Republic. When the Republic transitioned into the Galactic Empire, the Hegemony sustained its hostile relations and engaged in a conflict with them, while also encroaching upon Imperial territory.
Having surveyed the Empire, the Hegemony possessed knowledge of Imperial-class Star Destroyers, the capabilities and limitations of TIE starfighters, and other Imperial weaponry and technology. They leveraged this information in combat against Imperial forces.
The Attendants served the Hegemony during the Imperial Era, training other alien species in navigation to facilitate Grysk starships traversing the Unknown Regions.
The Grysk were a society built on warrior values, and while they had the characteristics of settled and centralized people, they were also described as generally nomadic. This was due to the view of no real fixed home, in which said perceptions were born out of their unfamiliar technology and cultural customs.
The Hegemony employed population control over the planets it ruled using a unique mental ability. This was achieved through a Grysk strike force learning about the targeted species and twisting their wills to a point where they would follow orders and further Grysks plans, even when the conquerors were not physically present. They succeeded to the point where the "client species," as the Chiss called them, would kill themselves with full knowledge that their masters would never even know if they had or had not. The Grysks interrogated a few members of the species to find out what mattered to them and their culture. They then used that against the whole of the species and continued to bend their will until all of their individualism is gone and then twisted them more into servants, meaning it only took several Grysks to rule over entire planets.
The Grysk Hegemony was situated in the Unknown Regions of the galaxy. Although they maintained homeworlds and displayed characteristics of a settled and centralized government, they were described as nomadic without a fixed home due to perceptions arising from their unfamiliar technology and wartime tactics. The Hegemony's location and area of influence brought them into conflict with the Chiss Ascendancy and other groups and species. During the Imperial Lothal campaign, they had already begun encroaching on the Galactic Empire's territory.
The Grysk Hegemony made its initial appearance, albeit unnamed, in the 2018 canon novel Thrawn: Alliances by Timothy Zahn. It was subsequently identified in the novel's sequel, Thrawn: Treason, also written by Zahn and released in 2019.