Ontano War

In 1246, Prince Louis Scavallo and Princess Eliza Sallea married, unifying the two houses together by marriage. Eliza's sister, Caterina, was already married to Prince John Maietta of Hellas, supposedly ensuring peace in the northern principalities for decades to come. Several weeks after the wedding, Prince John died suddenly, leaving no heir to carry on the Maiettan dynasty. The Maiettan War of Succession followed, lasting an entire winter and ending in turmoil with up to a quarter of the island's population dying of famine. Princess Caterina declared herself Princess Regent for her son, Prince John Maietta, and defeated rebel leaders swiftly. The Regent requested food supplies from Lessito, but was rejected by Prince Louis on the grounds that she wasn't the true sovereign of Hellas. A second rebellion began, and the Princess was almost murdered by her own guards, until she declared war on Lessito and called her banners. The navy of Hellas launched a surprise attack on the Scavallo territory of Ontano, and within three days had pillaged most of the island's coastal communities and bought a year's worth of crop back to the starving principality. House Scavallo declared war on Hellas and invaded the islands, razing towns to the ground and reportedly killing thousands in the streets. Caterina was captured and bought to Ontano to face justice before Prince Louis and her own sister.

Princess Eliza denounced her sister in Ontano and Prince Louis Scavallo ordered her to be burnt to death, a method of execution popular in the lands of Caterina and Eliza's fore bearers. Their father, Prince Carlos Sallea, committed suicide after his two children bough shame upon his house.

Battle of Tirera
Louis Scavallo immediately claimed the lands of House Sallea for his own, but his army was slow to regroup and House Calleas, a wealthy house from modern-day Monte Calida, moved its main army north and captured the Sallean capital of Tirera within a week of Carlo's death. House Scavallo marched an army to Tirera and sieged the town between 1251 and 1253. Both House Calleas and Scavallo lost "tremendous" numbers of men, according to scholars from the period, and the siege was one of the longest in northern history. Skirmishes between Hellas, Lessito and Monte Calida provinces lasted for another five years.

Treaty of Tirera
Prince John Maietta raised a rebel army and declared himself King of Hellas. By this time, House Celestine was becoming frustrated with the constant battling of its vassals. An assassin was placed in the new King's court and within four days, he had been stabbed. Papers from the Celestinian library state that the King of Cattala had sent the killer to Ionia. The King's son, Crown Prince Alfonso, visited Ionia, Almae and Seina - the capitals of Houses Maietta, Scavallo and Calleas respectively - and organised a peace treaty between all four houses in 1259. It was signed in Tirera, formally ending the siege of the city. House Calleas was granted easternmost lands from House Aroe and the western lands of the extinct Sallea house, whilst Scavallo was granted the eastern lands and the city of Tirera. House Maietta was pardoned, with the Crown Prince writing in memoirs that he believed they had suffered enough financial and military damage from the war.

Aftermath
The war that had begun in Ontano had spread across much of northern and eastern Cattala, affecting five royal houses and ending the line of House Sallea forever. House Scavallo gained northern and western territory that remain to this day a part of Lessito, and House Calleas expanded further north, becoming a major power in central Cattala and developed a near-monopoly over the trans-Cattalian trade routes.

It was the second war in twenty years for House Maietta, who had become one of the most powerful states in the kingdom after conquering Roumeli. The defeat and subsequent political turmoil that enveloped House Maietta weakened the principality forever, and it never regained the glory of the Expansionist era. The losses sustained in the Ontano War enabled the former royal house of Roumeli to rise up in rebellion and overwhelm the Maiettan army on the island, sparking the Roumelese Civil War.