Iapetus is the Titan personification of mortality. He is a son of Uranus and Gaia and father to four sons of his own, which he fathered in his union with Clymene, a daughter of Okeanos. Their sons are some famous individuals: Atlas, Prometheus, Epimetheus, and Menoetius.
People often see Iapetus as the ancient forefather of the human race, as his son Prometheus is the one who created mankind. The son of Prometheus would eventually end up being the ancestor of the human race. Zeus tried to destroy mankind with an epic flood, but Deukalion and his wife survived. After that, they started a dynasty that would be the foundation for the new human race.
Iapetus fought on the side of the Titans during their war with the Olympians. When Zeus and his family defeated them, Iapetus was locked away in the pits of Tartarus.