IAPETOS (Iapetus) was one of the elder Titanes (Titans), sons of Ouranos (Uranus, Heaven) and Gaia (Gaea, Earth). Led by Kronos (Cronus), Iapetos and his brothers ambushed their father as he descended to lie with Mother Earth. Krios (Crios), Koios (Coeus), Hyperion and Iapetos (Iapetus) were posted at the four corners of the world where they seized hold of the Sky-God and held him fast, while Kronos castrated him with a sickle. The Titanes were later deposed by Zeus and cast into the pit of Tartaros (Tartarus). According to Pindar and Aeschylus (in his lost play Prometheus Unbound) the Titanes were eventually released from the pit through the clemency of Zeus.
Iapetos (Iapetus) and his three brothers probably represent the four pillars of the cosmos which are described in Near-Eastern cosmogonies holding heaven and earth apart. Iapetos himself would have been the pillar of the west, a position later held by his son Atlas. When the Titanes were later cast into the pit of Tartaros - which Hesiod describes as a void beneath the foundations of the cosmos, where earth, sea and sky all have their roots - their cosmological role shifts from being supports of heaven to bearers of the entire cosmos.
Iapetos "the piercer" was probably also the Titan god symbolising mortality and the mortal life-span as his sons Prometheus and Epimetheus were the creators of mankind and all other mortal creatures.