(33-38/4) The Twilight War was a brutal conflict between rival factions of the kingdom of Valdor, specifically between two half-brothers; Eldan and Rhodan.
The war began because of a long-simmering sibling rivalry between the two sons of Valden the Conqueror; who, even as children, had always hated each other.
Upon their father's death, that hatred sparked into open warfare. After nearly six years of terrible bloodshed, the war finally ended with the Battle of Ossenfort; where Rhodan's forces were defeated, and he was forced to ask for terms.
Afterward, the kingdom of Valdor splintered into the kingdoms of Eldara and Rhodara; roughly two-thirds of former Valdorian territory was ceded to Eldara and the remaining one-third to Rhodara.
The Thannish civil war was called the "Twilight" War because Valden built a huge Thannish Empire throughout Corwyn, only to see it crumble upon his deathbed.