Nemertes (Ancient Greek: Νημερτής) is one of the fifty Nereids, marine-nymph daughters of Nereus and the Oceanid Doris. Hesiod closes his Nereid catalogue by naming her as the sister who has the nature of her deathless father — unerring and truthful like the Old Man of the Sea. Homer lists her among the sisters who mourn with Thetis for Achilles' grief over Patroclus.
Adapted from Wikipedia, "Nemertes (mythology)" · CC BY-SA 4.0
I.Among the Nereids
Hesiod's Theogony places Nemertes near the end of the fifty-daughter roll of Nereus and Doris, after Neso, Eupompe, Themisto, and Pronoe, and explicitly notes that she has the nature of her deathless father. Apollodorus and Hyginus also include her among the Nereids.
Like her sister Apseudes she is associated with truth-telling and good counsel. Some modern handbooks identify her with another catalogue Nereid, Neomeris, but the atlas keeps Nemertes as the Hesiodic sea-nymph of the truthful epithet.
II.In the Iliad
When Thetis cries out in sympathy for Achilles after the death of Patroclus, Homer gathers the Nereids in the bright cave. Nemertes appears in that mourning throng beside Doris, Panope, and Galatea — a catalogue presence without a separate adventure of her own.
III.Homonyms
This atlas entry (nemertes-nereid) is the Nereid. She is not Nemesis, the goddess of retribution, nor any separate personification of truth outside the Nereid catalogues.