The Fall of Kooluk was an event that brought the end to the Kooluk Empire in SY 309. It happened a short time after the Empire lost the Island Liberation War and the fort of El-Eal was destroyed by the Liberation Navy. The Kooluk Empire was already in decline, focusing only on defense, and divided by two major factions; the Patriarchal Faction and the Imperial Faction. A member of the Patriarchal Faction known as Iskas conducted illegal research on Rune Cannons inside of the newly formed Island Nations territory, going against the Peace Treaty issued after the Island Liberation War. This caught the attention of the King of Obel, Lino En Kuldes, and Rune Cannon researchers from the Scarlet Moon Empire, one of them a young man known as Kyril, who sought to destroy these weapons.
Iskas, on his research, found the effects of the "Evil Eye", a modified version of the common Rune Cannons with the power to transform human beings into Fishmen. Iskas then used these powers to create a Civil War inside the Empire between the Patriarchal Faction and the Imperial Faction, and was able to transform the Emperor Julius and the Crown Prince Martin themselves into Fishmen.
The Princess of the Empire, Corselia, the Scarlet Moon Researchers, and several veterans of the Island Liberation War managed to stop Iskas's plan from taking over the Empire, but with the government shattered and the Empire in a steep decline, the successor to the throne, Princess Corselia, decided to let the empire walk to its end.