Once an ordinary human, Cleito became the lover of the God of the Sea, Poseidon, and he granted her godly powers and created the Kingdom of Atlantis for her, leaving her to rule in his absence. She then became known as the Sea Goddess Amphitrite.
But she went mad with her power and found a new lover, a gigantic serpent known as Oceanus. She had the Atlanteans rebel against Poseidon which gained his utmost fury. He destroyed Atlantis and assumed he killed Amphitrite as well.
She however survived and renewed her plans to defeat Poseidon and take over as ruler of the sea.