War of Kin

The War of Kin, sometimes known as the Hosaq Civil War, was a major series of conflicts which embroiled the Hosaq Empire during the fifth century of the New Age. Having lasted half a century, it is considered to be one of the longest internal conflicts in recent history. Although the Long Decline had begun a century earlier, the War of Kin is generally considered to have doomed the Empire to lose its position as sole hegemon of Venail.
Following the death of Yazhnan II in 424 NA, his infant son Yeren I became Emperor, under the regency of his maternal uncle, Elqran the Stern. Yeren would succumb to disease himself in 428 NA, sparking a succession crisis. In the months following his death, three pretenders arose. Elqran, who at the time of Yeren's death was on campaign in Heremopia declared himself Regent-Protector, de facto attempting to seize the throne for himself. He was able to amass support among the traditional Hosaq nobility and the Hosaq Imperial Army. Yeren's sister, Manyria I proclaimed herself Empress. With the help of the powerful family of her bethrothed, she was able to secure support in Hosaq itself. Finally, the old Emperor's young cousin, Manar IV proclaimed himself Emperor as Yazhnan's closest male relative. He spent the first years of the conflict building up support in the Duchies. 
By the end of the conflict, all three initial pretenders were dead. Ultimately, Manyria's son would take the throne as Manar V in 461 NA and would fight off various pretenders and rebels for over a decade. Elqran was defeated and killed in the field at the Brass Hills in 446 NA, but his son Yeren III continued fighting for another fifteen years. Manar IV abandoned the conflict in 456 NA following the secession of his principal power base in the Duchies in 453 NA. The same year, he invaded the Sil Hur Remnant and founded the independent Kingdom of Silur, from which he planned to prepare an invasion of the Empire. His plans never came to fruition as he waq poisoned in 265 NA. 
Despite the conflict primarily being an internal one, it affected all the lands within the Empire and many outside. The war effort increased tax burdens, levies and reduced trade. This would lead many parts of the Empire to secede during the war and in its immediate aftermath. The 450s saw an unprecedented wave of secessions as the Duchies, Southern Realms, Yondarin and much of Western Aislinvem seceded. Many believe that the further weakening of the Empire by the conflict led to the Great Concession of 532 NA.