Coriantumr was a Jaredite prince, a son of Omer, born while Omer was held in captivity. Omer’s son Jared had rebelled against him, gained half the kingdom, and carried his father into captivity, where Omer remained for half his days; during that time Coriantumr and his brother Esrom were born to him (Ether 8:4-5). Angered by Jared’s actions, Coriantumr and Esrom raised an army and attacked him by night, destroyed his army, and were about to kill him when Jared begged for his life and offered to give up the kingdom; they spared him and restored the throne to Omer (Ether 8:6).
Jared, grieving the loss of the kingdom, conspired through his daughter with Akish to take it back, and Akish’s secret combination overthrew Omer (Ether 9:3, 12). The Lord warned Omer in a dream to depart, and he left with his household, “his sons and his daughters, and all his household, save it were Jared and his family” (Ether 9:3) — a flight that would have included Coriantumr. Akish then turned on Jared and had him killed, and a war broke out between Akish and his sons that destroyed nearly all the people of the kingdom, leaving only about thirty souls together with those who had fled with Omer’s house (Ether 9:12).