|“||Curse that upstart, I was here first.||”|
Nereus is the Greek god of the sea's rich bounty of fish, but he is better known as the "Old Man of the Sea" and is said to know everything, even tidbits of information concealed from the Oracle of Delphi.
Like many of the other sea-gods, Nereus was a master shapeshifter, however, not much is known about his past, though he claims to have existed before Poseidon, whom he refers to as an "upstart". If captured, he will allow his captor to ask him one question.
Nereus, a sea-deity, was a son of Gaea, by Pontos. Apollodōrus gives him Terra for his mother. His education and authority were in the waters, and his residence, more particularly, was in the Aegean seas. He had the faculty of assuming what form he pleased. He was regarded as a prophet; and foretold to Paris the war, which the kidnapping of Helen would bring upon his country.
When Hercules was ordered to fetch the golden apples of the Hesperides, he went to the nymphs inhabiting the grottoes of Eridanus, to know where he might find them; the nymphs sent him to Nereus, who, to elude the inquiry, perpetually varied his form, till Hercules having seized him, resolved to hold him until he resumed his original shape, in which he yielded the desired information.
Nereus had, by his sister Doris, fifty daughters called Nereids. They dwelt in the Aegean Sea in ancient times, but he moved to the San Francisco Bay with the gods who moved to New York. Hesiod highly celebrates him as a mild and peaceful old man, a lover of justice and moderation.
Following advice from Apollo, Percy Jackson found Nereus on the docks of San Francisco, California, after dressing up in old clothes found by Zoë Nightshade. As Nereus is tired of being sought by demigods for answers to their questions and just wants to be left alone, Percy has to catch him long enough to ask one question. However, Percy tricked Nereus into jumping into the water with him holding on, making Percy stronger and overpowering him. During the fight, Nereus shape-shifted into different types of animals, including a seal, a killer whale, and an eel to shake off Percy's grasp. However, his tossing and shape-shifting didn't work well leaving Nereus confused as to why Percy didn't drown at all, and Percy revealed that he was a son of Poseidon, much to Nereus' dismay. He eventually conceded the struggle and agreed to answer the hero's question. Percy asked him for the location of the monster that Artemis, goddess of the moon and the hunt, had been tracking. Nereus said that the question was too easy and simply pointed to the Ophiotaurus, the creature that had been following Percy and his friends during the events of their quest. In Percy's confusion, Nereus changes into a goldfish and escapes into the sea.
When Percy, Hazel Levesque, and Frank Zhang are sailing out of San Francisco Bay, Hazel becomes so sea sick that she thinks she is hallucinating when she sees him as an old homeless man hanging around a bunch of sea lions. When he sees Percy, he remembers their previous encounter, and points his finger at Percy as if to say, Don't even think about it.
Nereus is described as looking like Santa Claus's evil twin, he is fat and has a white beard that has turned a shade of yellow. Nereus was wearing pajamas and a fuzzy bathrobe. He is also described as having a bad smell, like hot seaweed, dead fish and brine. Percy said that "If the ocean had an ugly side, this guy was it".
Nereus possesses the standard powers of a god.
- Hydrokinesis: As a sea god, Nereus has absolute control and divine authority over water as well as the sea. He has the same hydrokinetic powers as Percy's, though possibly to a far greater and more advanced level.
- Omniscience (possibly): Given how Nereus knew things that were unknown to even the Oracle of Delphi, as well as his ability to give accurate answers to any questions that his captors could pose, it is possible that he knew everything and anything indefinitely.
- Shapeshifting: As shown in The Titan's Curse, Nereus was a masterful shapeshifter, transforming into a seal, killer whale, eel, and goldfish while fighting Percy. It was also possible that he was able to shapeshift into inanimate objects, though he did not display it.
- With the Oceanid Doris:
- In some stories, other gods take the role of the Old Man of the Sea. These include Proteus, Triton, Pontus, Phorcys or Glaucus.
- On the fifth voyage of Iraqi folklore character of Sinbad the Sailor, the titular encountered a monstrous Old Man of the Sea. The Old Man of the Sea enslaved Sinbad after he was shipwrecked, he would ride on his shoulders with his legs twisted round Sinbad's neck and will not let go, riding him both day and night. But then Sinbad made wine and tricked the Old Man into drinking some. After he has fallen off, Sinbad kills him then escapes.
- Nereus appears to have been the personification of the sea in its calm and placid moods.
- After Poseidon, Nereus seems to be the most important of the sea-deities the Greeks worshiped.
- Nereus' name means "wet one".