The Mitth Ascendancy, known as the Eighth Governing Family since 27 BBY, was a prominent Chiss lineage and an integral component of the Nine Governing Families within the Chiss Hierarchy. The Mitth family had rivalries with the Irizi lineage and the Ufsa lineage, while maintaining an alliance with the Obbic lineage.
A youthful Chiss individual, who would later become the Galactic Empire's High Admiral Thrawn, was integrated into the family during his early years.
The actual background of the Mitth lineage was a closely guarded secret accessible only to key family members, such as the Clan Leader. The family's past was intertwined with an extraterrestrial weapon referred to as the Starflash. The Mitth family commanded a naval force that augmented the Ascendancy's defensive capabilities during the Grysk agent "Jixtus"'s scheme to bring about the nation's downfall.
The Mitth lineage traces its roots back to the Chiss birthplace, the planet Csilla. Even after the world underwent a freezing event and the majority of Csilla's inhabitants relocated to other planets within the Ascendancy, the Mitth family preserved their central base at the Mitth lineage estate, situated beneath their ancestral territories within Csilla's primary city, Csaplar.
During the Ultimate Offensive on Csilla, the Chiss Hierarchy faced imminent destruction at the hands of its adversary. It was at this moment that the Stybla Clan Leader recalled the existence of a devastating weapon known as the Starflash. Twenty Mitth warriors volunteered to operate the weapon, including the four sons of Mitth'omo'rossodo. Starflash was discharged towards Csilla's sun, resulting in a counter-blast that obliterated both the invading fleet and the weapon itself, leading to the demise of all its operators. As a result of this noble sacrifice, the Mitth were elevated to the status of a Governing Family, and Thomoro was bestowed with the Stybla honorific "odo". Furthermore, the Mitth lineage emblem was redesigned to depict a radiant sun.
In the time leading up to the Lioaoin pirate incursion, the Mitth family welcomed a young Chiss named Kivu'raw'nuru into their ranks as a meritorious adoptee originating from his home planet of Rentor. Unbeknownst to Mitth'urf'ianico, the Aristocrat responsible for enlisting Vurawn, Vurawn was to be reassigned to the Mitth family under the explicit request of Clan Leader Mitth'oor'akiord himself. During Vurawn's time as a recruit, Clan Leader Thooraki also insisted on recruiting former skyfarer Al'iastov into the Mitth.
Around the assault on Csilla towards the conclusion of the Clone Wars, the Mitth family was engaged in a competitive rivalry with the Ufsa family to secure a mining venture on Thearterra. During this period, the Mitth family was guided by Clan Leader Mitth'oor'akiord, who demonstrated a keen interest in recruiting and integrating promising Chiss individuals into the Mitth lineage.
Clan Leader Thooraki attended Mitth'ali'astov's Trials at the Mitth family estate, and he personally congratulated the mentor as a Trial-born of the Mitth. As she nearly reached the peak of the mountain that marked the end of the Trials, Thalias encountered an elderly man with pale skin due to age. Around the mountain's summit were commemorative staffs honoring deceased Mitth family Councilors, Spokespersons, and Clan Leaders, along with their accomplishments and those they recruited or elevated within the family. The elderly man asked the mentor for her opinion on a particular memorial staff adorned with many smaller staffs nearby, to which she responded that it was impressive. The elder laughed and responded that such displays were only impressive to those impressed by pure numbers, and that quality of recruits was more important than quantity. At that point, Thalias recognized the elder as Clan Leader Thooraki. The Clan Leader told the mentor that Thrawn would bring great glory and renown to the Mitth and someday be his crowning jewel, and Thrawn's staff would stand next to Thooraki's own adorned memorial staff one day. He told Thalias that he personally arranged for both Thrawn and her to be rematched into the Mitth family, and asked Thalias to look after Thrawn and protect the officer from enemies within the Ascendancy and possibly the Mitth family itself. Thooraki worried that an enemy of Thrawn might try to succeed him as Clan Leader once he died.
Indeed, Thrawn had adversaries within the Mitth. Chief Councilor Mitth'urf'ianico, the very Aristocrat who recruited Vurawn to the Mitth from Rentor, harbored a grudge against Thrawn. In collaboration with Irizi family Councilor Zistalmu, Councilor Thurfian plotted to undermine Thrawn's career. During his official duties in the Council, Thurfian sought to advance Mitth interests but also sabotage Thrawn. Thurfian was promoted to Chief Councilor by ingratiating himself to the political establishment of the Mitth family and the Council, and had an eye on the Speakership, then held by Mitth'ykl'omi. During the Nikardun military campaigns, Chief Councilor Thurfian arranged to send Mitth family spies to learn the secrets of the Great Stybla family, renowned as merchants and shippers.
Upon the passing of Clan Leader Thooraki, Chief Councilor Thurfian was selected by the Matriarchs and Speaker as his successor. Thurfian had not even set his sights on the Clan Leadership Position, and believed that perhaps Speaker Thyklo may have succeeded Thooraki. Nevertheless, Clan Leader Mitth'urf'ianico was highly pleased with his new role and powers.
With the exception of the individual character Mitth'raw'nuruodo (Thrawn), the Mitth family made its initial appearance in the 2020 novel Thrawn Ascendancy: Chaos Rising, the introductory volume of The Ascendancy Trilogy penned by Timothy Zahn.
There exists an inconsistency pertaining to the color associated with the Mitth family. Senior Captain Thrawn is seen wearing a burgundy shoulder patch in Thrawn: Alliances, which aligns with Thrawn's portrayal in Star Wars Legends as depicted in the 2006 novel Outbound Flight, however, Councilor Mitth'urf'ianico is shown wearing a yellow outerwrap robe with a prominently displayed Mitth family crest in the novel Thrawn Ascendancy: Chaos Rising, and a poster featuring Councilor Mitth'ras'safis included in the Barnes & Noble exclusive edition of the novel Thrawn Ascendancy: Lesser Evil portrays him wearing gray-and-yellow official garments. Within the Star Wars Legends continuity, the color yellow was previously established as the designated color for the Chaf family in Zahn's 2004 novel Survivor's Quest.