In 84 NE, Renii Vatio ascended to the Sular throne. In the years following, a grand purge was carried out on several levels of the Sular bureaucracy, although also extending into the remaining nobility. It targeted anyone who either belonged to a rival imperial house as well as military brass Vatio viewed as foreign. Although harsh, Vatio believed the purge was necessary to "stop the bleeding" and halt the decline of the monarchy's power.
The purge, sometimes called "The Night of Gunpowder," also saw Vatio's first conflict with the Cult of the Runes. Their ecclesiastical protections ensured the purge was mostly ineffective on their ranks, much to his chagrin.
Background
The Sular Monarchy had been weakened by centuries of clashes and disputes between rival houses. Loyalty to, or faith in, the monarchy completely crashed during the final years of the Sular Supremacy, as civil wars became increasingly common. No matter how strong a claim to the throne was, the Secret of Empire ensured that the army played kingmaker. Eventually, the houses became powerful enough to effectively split the army into factions of its own, or raise private ones on short notice.
With the fall of the Supremacy, the Renii house emerged as the dominant faction. Being the only house actually originating from the remaining Sular Empire (and thus, being nearest to the original territory of Sul), they prided themselves on being the only "truly Sular" dynasty around. The other houses either dissolved or were dramatically weakened, but their claims persisted. However, the Sular Monarchy was a shadow of its former self, now reigning over a small empire in almost constant turmoil.
But the Cult of the Runes had lost almost no power over the island. The Sular Emperor became a puppet of the First Mage and his Nightmare Mages. This persisted for three emperors, until finally Vatio's late father broke the monarchy free from their control again.
When Vatio became the new Sular Emperor in 84 NE, he sought to stop this decline, but needed to secure his own position first. He completed the partitioning of the Kingdom of Jarine started by his father, establishing the Sular Empire as a force to be reckoned with once again. He stoked xenophobic fears that foreigners had caused the fall of the Supremacy, all the while re-asserting his house's position as the only "natively Sular" house.
Purge
Three years later, Vatio made his move. First, he targeted the military's higher ranks. Generals and officers originating outside the Renii Plateau (the heartland of the remaining Sular Empire) were deposed and arrested. He alleged that a foreign conspiracy rested within the military's ranks, supported by both the Vellen Empire and the Hegemon. Anyone who questioned or balked at supporting these fantasies were arrested as well.
Then, with the remaining military loyal to his xenophobic ideas, he sent them across the empire to purge the nobility. Each cohort carried a list of names, every one of them a member of a rival house. Vatio accused these "foreign" houses of being at the heart of the conspiracy.
For the first time, these legionnaires carried new hand cannons, largely ineffective but immensely intimidating. However, the soldiers had yet to be fully trained in how to use them, resulting in chaotic gunfire that scarred the night with sounds of handheld explosions. This part of the purge was dubbed "The Night of Gunpowder" by locals in Ceveris, and the name stuck.
Those arrested were tried on charges of treason, beaten into confessions or simply found guilty on falsified evidence before xenophobic juries/judges.
High-ranking members of The Cult of the Runes were also targeted, but to limited effect. The power of the monarchy was still totally unable to break that of the clergy, frustrating Vatio's efforts. Furthermore, members of the clergy often protected what foreigners they could, particularly within the College of Runes.
Aftermath
The purge devastated the rival houses, effectively breaking their power once and for all. However, it shook confidence in Vatio's young reign, propped up only by his successful annexation of Jarine and the xenophobic fervor he unleashed.
The Cult of the Runes had been surprised by Vatio's open hostility towards their ranks, but now viewed him as an enemy. The feeling was mutual, with Vatio now viewing them as the sole remaining opposition to his restored authority. To break them, he planned to go directly for their jugular; he would have to corrupt and conquer the College of Runes.