Nereus

In Hesiodic genealogies Nereus is the eldest son of Pontus (the Sea) and Gaia (the Earth). He becomes father, with the Oceanid Doris, of fifty daughters known as the Nereids and of a son Nerites in some later accounts. As an archaic sea-personification he occupies a primordial place in Greek cosmogony, an ancestral marine power later overlain in prominence by Olympian deities such as Poseidon.

Literary tradition describes Nereus as an aged, bearded sea-god — Hesiod calls him trustworthy and gentle — and Attic vase-painting commonly depicts him as a draped torso issuing from a long, coiling scaly fish-like tail, often holding a staff of authority. He is visually and thematically allied with the broader 'Old Man of the Sea' iconography found in Greek art.

Sources portray Nereus as truthful and morally steady (Hesiod's 'tells no lies') and as possessing prophetic knowledge. He shares with other 'Old Man of the Sea' figures the motif of shapeshifting: heroes who could seize such a sea-elder while he was changing form could compel prophetic speech. Literary tradition therefore treats him as a helpful prophetic source for heroes (parallel to Proteus) rather than as a malignant force.