The climactic battle for Csilla, a pivotal battle, transpired circa 4300 BBY. This confrontation marked the culmination of a significant war fought between the Chiss Ascendancy and a ruthless enemy within the Unknown Regions. The Chiss Defense Force had retreated to their capital planet, Csilla. Despite facing heavy losses, the Chiss possessed a concealed superweapon known as the Starflash. This ancient alien energy weapon was secretly guarded by the Stybla family. The Starflash was designed for a single use only, requiring twenty operators, which meant certain deaths for all involved. Warriors from the Mitth family volunteered, willingly giving their lives to save the Ascendancy.
The weapon, along with the twenty Mitth members, collectively called the Starflash team, were placed aboard a heavily fortified ship. This ship was then dispatched into the heart of the enemy fleet. As the enemy fleet approached, the Mitth warriors activated the weapon. This unleashed a powerful surge of tachyonic and lightspeed energy directed at Csilla's sun. This action triggered a return blast, thousands of times stronger, back towards the weapon's origin. The ship and the enemy fleet were obliterated, securing victory for the Chiss. However, this energy surge into the sun destabilized its core, leading to a gradual cooling process over subsequent decades. This cooling eventually rendered Csilla's surface uninhabitable. In recognition of their sacrifice, the Mitth were elevated to the status of a ruling family. Mitth'omo'ross, the Patriarch of the Mitth, whose core name was "Thomoro," was bestowed the Stybla honorific "-odo," and adopted the name "Mitth'omo'rossodo." Furthermore, she earned the title "The Tragic" in honor of her sons' sacrifice.
Around 5000 BBY, during a period of extensive exploration by the Chiss Ascendancy in the Unknown Regions, an alien superweapon, known as Starflash, was brought back to the Ascendancy. Along with the weapon, a detailed report outlined its function, operation, and the potential consequences of its use. The weapon was designed for single use only, and required twenty individuals to operate, making it a suicide mission for all participants.
The Chiss ruling Stybla family constructed the Bastion, a secure facility to house the weapon, with the hope that it would never be needed. However, around 4300 BBY, the Chiss found themselves engaged in a war against a relentless enemy. This enemy had overrun the Ascendancy's outlying [worlds](/article/planet], forcing the Chiss Defense Force to retreat back to their capital planet, Csilla.
The enemy had focused their entire [fleet](/article/fleet] to bear on Csilla, with the intent of destroying the planet and eradicating the Chiss species. However, the Stybla family Patriarch recalled the existence of the Starflash and decided to deploy it, despite its never having been used before. Twenty individuals were needed to operate it, and warriors from the Mitth family volunteered, including the four sons of Mitth Patriarch Mitth'omo'ross, whose core name was "Thomoro." All four sons insisted on sharing the same risks as the other Mitth, sacrificing themselves to save the Ascendancy. The Starflash team and the weapon were then loaded onto a heavily armored ship and sent directly into the path of the approaching enemy fleet.
As the enemy fleet drew near, the Mitth warriors activated the Starflash. The weapon emitted a massive burst of tachyonic and lightspeed energy towards the surface of Csilla's sun, which in turn triggered a return blast of immense power back at the weapon. The resulting explosion destroyed the enemy fleet, the Starflash, and the twenty Mitth warriors, leading to a Chiss victory in both the battle and the war.
Following the annihilation of the enemy fleet, the Ascendancy was able to reclaim its outer territories from the small garrisons left behind by the enemy. The Patriarchs of the ruling families chose to keep the details of the assault secret, with only the Patriarch and their Senior Aide knowing the full truth. The Senior Aide was then tasked with passing the truth to their Patriarch's successor. Despite understanding the Starflash's operational mechanics, the Chiss had not anticipated the extent of the damage it would inflict on Csilla's sun. While initial reports indicated that the Starflash blast only affected the sun's surface, the disruption reached deeper into the sun's core. Over the following decades, the sun began to [cool](/article/temperature], rendering the surface of Csilla uninhabitable. The planet's inhabitants were forced to relocate to underground caverns or leave the planet entirely.
In addition, the Aristocra, the mid-level members of the ruling families, were deeply moved by the bravery and sacrifice of the Mitth family. As a result, they elevated the Mitth to the status of a Ruling Family. This event also led to the adoption of a blazing sun as the Mitth family crest. Patriarch Thomoro was granted the Stybla family honorific "-odo," which in the Stybla native language Tybroic signified "a guardian or protector who had proven worthy of the most extraordinary respect," in recognition of her sons' sacrifice. She was also given the epithet "The Tragic," and adopted the name Mitth'omo'rossodo "The Tragic."
Thousands of years later, by 19 BBY, the battle had become known as the "Final Assault on Csilla," and the truth surrounding the event had been obscured over time. Stybla'mi'ovodo "Lamiov," the Stybla Patriarch, revealed the true details of the assault and the Starflash to Mitth'ras'safis "Thrass," a member of the Mitth family Syndic, and Mitth'raw'nuruodo "Thrawn," a Senior Captain. Additionally, a conspiracy theory emerged among academy [cadets](/article/cadet]. They believed that two of the Chiss families had secretly collaborated with the invaders to bring about the Ascendancy's downfall.
The Final Assault on Csilla was referenced in flashbacks within the 2021 novel Thrawn Ascendancy: Lesser Evil, which served as the concluding chapter of Timothy Zahn's Star Wars: The Ascendancy Trilogy.