Born the sole child of Emperor Pelagius Septim III and Empress Katariah Septim, Cassynder inherited the throne on the death of his mother. Already middle-aged and in poor health, he left the care of High Rock province to his half-brother Uriel Lariat, though as the only true blood relation of Pelagius Septim III, and thus Tiber Septim himself, he was pressed into accepting the throne. He died after only two years of rule. His half-brother Uriel Lariat succeeded him and was crowned Uriel Septim IV.
His mother Katariah was a Dunmer, while his father, Pelagius Septim III received Imperial blood from his father Magnus and Altmer blood from his mother, Utheilla, making him a "tri-breed." But because of the way interbreeding works in The Elder Scrolls he was most likely considered a Dunmer, because the child generally takes the race of the mother.
- According to Brief History of the Empire, Book II, he would have died in 3E 201. The Third Era Timeline contradicts this, however, stating he died in 3E 202.
|Emperor of Tamriel|
|Katariah||3E 200–3E 202||Uriel Septim IV|
|King of Wayrest|
|Years Prior Emeric of Cumberland||3E ?–3E 200||Uriel Septim IV|