He is described as the wise and unerring old man of the sea, at the bottom of which he dwelt (Theogony of Hesiod 233).
His empire is the Mediterranean or more particularly the Aegean sea, whence he is sometimes called the Aegean. He was believed, like other marine divinities, to have the power of prophesying the future and of appearing to mortals in different shapes, and in the story of Heracles he acts a prominent part, just as Proteus in the story of Odysseus, and Glaucus in that of the Argonauts.
Virgil mentions the trident as his attribute, and the epithets given him by the poets refer to his old age, his kindliness, and his trustworthy knowledge of the future.
In works of art, Nereus, like other sea-gods, is represented
with pointed sea-weeds taking the place of hair in the eyebrows,
the chin, and the breast.