Eluno

Eluno is a Naiad. Well, he was. Erebos cursed him into a hideous fish form and forced him to live high in the mountains of Akros away from the waters! Thassa dare not interfere too much, but she graced him with a rainbow, Nyx-like piscine form, and she said if he could find his way home she would revert his form.

Eluno was cursed so severely because he was caught scouting on Thassa's behest. He ended up finding an underwater entrance to the Underworld which neither Erebos nor Athreos appreciated.

Found being hunted by—or perhaps messing with—a cyclops, the party rescued Eluno and accepted the quest to bring him back to The Siren Sea.