In the year 4985 BBY, a devastating purge was initiated by Yaru Korsin, the leader of the Lost Tribe of Sith residing on Kesh. This purge targeted the forty-five pureblood Sith who were present on the planet. The catalyst for this event was a scheme devised by Ravilan Wroth, the leading figure among the Sith species within the Lost Tribe. Wroth's plan involved poisoning the water supply of the city known as Tetsubal. His intention was to compel the Lost Tribe's leadership to prioritize finding a means of escape from the planet, where the Sith had been marooned for fifteen years. However, Seelah, the wife of Yaru Korsin, uncovered Wroth's plot and falsely implicated him in similar deadly incidents that had occurred in nearby towns. Convinced that Wroth and the purebloods posed a threat that needed to be eliminated, Korsin launched a purge that unfolded over the course of a single night. Despite the purebloods' valiant efforts to defend themselves, they suffered increasing losses. Ultimately, Wroth was captured and held as a prisoner as the last remaining purebloods made their final stand against Yaru Korsin and his lieutenants high up in the Takara Mountains. After the last holdouts were killed, Wroth was executed by Jariad, the son of Seelah Korsin, and the corpses of the deceased were displayed publicly in the city of Tahv. As a result of the purge, all of the non-Human members of the Lost Tribe of Sith, with the exception of Gloyd, the Houk friend of Yaru Korsin, were eradicated from Kesh.
Around 5000 BBY, the Sith starship called the Omen experienced a navigational failure during a hyperspace jump, leading to a crash landing on the isolated planet of Kesh. Following a tumultuous initial period in the mountains where the Omen had crashed, the Sith encountered a relatively unsophisticated civilization of Keshiri natives. By presenting themselves as the Keshiri gods, the Sith quickly established themselves as the rulers of Kesh. The Omen's crew included a significant number of pureblood Sith, but only fifty-seven remained when the Sith emerged from the mountains. By 4985 BBY, twelve had died due to various unfortunate circumstances, and no pureblood Sith children had survived beyond a day. Meanwhile, the Human population within the Lost Tribe of Sith thrived. Ravilan Wroth was the most prominent pureblood member on Kesh, often representing his people before Lost Tribe leader Yaru Korsin.
However, Wroth harbored his own discontent with the Lost Tribe, desiring that Korsin withdraw his people from Keshiri affairs and focus on finding a way to leave Kesh. To achieve this, Wroth devised a plan: during a research expedition to the Ragnos Lakes region, Wroth decided to poison the water supply of the city of Tetsubal to create the illusion of a deadly virus sweeping across the planet. Wroth successfully executed his plan, using the compound cyanogen silicate to kill all 18,000 Keshiri residents of Tetsubal. However, his plan was discovered by Seelah, the wife of Yaru Korsin, who, already prejudiced against the purebloods, decided to frame Wroth for further crimes. Korsin replicated the deadly act in seven other towns near Tetsubal, resulting in the deaths of hundreds of thousands of Keshiri. Seelah presented her husband with evidence that Wroth and his retinue had visited all those towns recently, as well as proof that he had access to cyanogen silicate. Convinced of Wroth's involvement in the deaths, Korsin declared that it was time for the non-Human members of the Lost Tribe to be eliminated.
In a single night, all of the "Fifty-seven," as the non-Human Sith of Kesh were known—except for the Houk Gloyd, a close friend of Yaru Korsin—were killed. The Fifty-seven did not go quietly, fighting the Lost Tribe assassins throughout the darkness in the mountains, though they could not withstand the attack for long. A young sentry was trapped and killed, never abandoning his post until the bitter end. Another prominent member of the Fifty-seven, the cyborg translator Hestus, was personally brought down by Seelah Korsin herself. The dead were beheaded and put on display in a plaza in the city of Tahv, even while the remnants of the Fifty-seven still held out against Yaru Korsin and his chief lieutenants. The final living members of the Fifty-seven were driven to a last stand high in the Takara Mountains, close to the Omen's original crash site. No quarter was given, and Yaru Korsin threw any who surrendered over the side of a cliff. Meanwhile, the wounded Ravilan Wroth was brought to the plaza where those already killed were displayed. Confronted by Seelah Korsin, Wroth admitted his complicity in the deaths at Tetsubal, but not in any of the other cities. Revealing her deception, Seelah took credit for those deaths, as well as the deaths of all the infant pureblood Sith who had been born on Kesh since the Omen's crash, saying that Wroth and his people would have done the same to Seelah and her kind eventually. With that, Jariad Korsin, Seelah's son, emerged from the darkness and killed Wroth, completing the purge.
Following this, every non-Human crewmember of the Omen, excluding Gloyd—who himself would meet his end alongside Yaru Korsin in a lightsaber duel ten years later—was killed. Unbeknownst to the Lost Tribe, their purge was secretly supported by a Keshiri resistance movement dedicated to overthrowing Sith rule on Kesh. Tilden Kaah, a secret operative of the resistance movement and the personal attendant to Seelah Korsin, immediately informed resistance leader Adari Vaal after the purge's completion. Although the Lost Tribe experienced a population decline due to the purge, it was more than compensated for by a rapid increase in births over the next decade. In the years following the bloodshed of the purge, Yaru Korsin viewed the purge as an unfortunate but ultimately necessary event, believing that a homogenous Lost Tribe was easier to govern. Knowledge of the Fifty-seven or the purge was largely lost, as Seelah Korsin took steps to erase them from history. Nevertheless, Keshiri tales persisted about "deformed" crewmembers of the Omen and their elimination. By 3000 BBY, there was an active political faction on Kesh known as Force 57 that was comprised of physically imperfect members of the Lost Tribe, who revered Ravilan Wroth and the original Fifty-seven.
The initial depiction of the purge of the Fifty-seven can be found in John Jackson Miller's 2010 eBook, Lost Tribe of the Sith: Paragon. The event received further mention in two subsequent sequels, Savior and Pantheon, as well as in the 2012 reference book The Essential Reader's Companion. In his production notes for Paragon, Miller revealed that he utilized the purge as a "story springboard" to transition the Lost Tribe from its more diverse form, as seen in the Sith of the Tales of the Jedi comic book series, to the homogenous kind found in the later Fate of the Jedi novels.