Korrinth is a nation that developed during the early Second Chaotic Period on the north-western end of the Greater Continent. They split from the Marcon Alliance shortly before the destruction of the marcons at the hands of the old Gudersnipe Army.
Like all of the Marcon Alliance, Korrinth was utterly devestated by attacks from the Gudersnipe Army. They were, however, quickly able to organize and rebuild, errecting new Mage Towers within years of the attack. The Korra believed the rest of the Marcons had been killed, and thus did not attempt to contact their brethren.
In the confusion, many former slaves gained their freedom, and even attained high positions in the new government. This would forever change the makeup of the Korra, making them an independant nation, and not just a bunch of Marconian stragglers.
Though they did not adhere to the stricter tenants of Marconian beliefs, the Korra still practiced slavery and held women in little reguard. Polygamy was still common, but women had some rights, and as early as B.G.A. 250, Korrinth had laws barring the sale of free women as brides.
Fall of Korrinth
Eieber set his sites on Korrinth in the third year of his Long March (B.G.A. 4), after the Battle of Korrasign at the beginning of the year. The country set several problems for conquest. Along the Sword Coast, a massive armada of ships and a series of island fortresses made attack by sea impossible. To the east, Korrinth was bordered by impassable mountains and a massive desert. The only avenue of attack was through Two-Fang's Pass, a heavily-fortified series of mountains.
Seeing no easy way through, Eieber enlisted the help of Finley Ray, a powerful Anomancer who controlled an army of dragons. The dragons simply flew Eieber's army over the Deadlands and into the heart of Korrinth, where they took the capital city in just three weeks. The dragons were then sent to destroy the Korrinth navy, and the war was essentially won.
Korrinth was not allowed to retain its sovereignty, and at Eieber's direct order, was kept under martial law until A.Y. 180, when its citizens were allowed to vote in free elections for the first time. The country was renamed Oncathula, and made a province of the Alliance.
Oncathula remained the common name until the end of the Golden Age and the Ninety-nine-years war. While the Alliance's central power structure crumbled, the people of Oncathula declared independence and changed it's name back to Korrinth. Often called "Modern Korrinth" to signify the difference between the old and new, the country would retain a certain degree of independence while slowly being absorbed back into the Alliance during the Second Age.
Modern Korrinth is nominally an independent country, but has such strong social, political, economic, and military ties to the Alliance that it is effectively just part of the whole. The massive social changes brought about by Eieber's occupation were did stick, and Modern Korrinth is largely indistinguishable from most other parts of the Alliance.