This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Nereid (Greek)
In Greek mythology, the Nereids or Nereides are sea nymphs (female spirits of sea waters), the 50 daughters of the 'Old Man of the Sea' Nereus and the Oceanid Doris, sisters to their brother Nerites. They often accompany Poseidon, the god of the sea, and can be friendly and helpful to sailors (such as the Argonauts in their search for the Golden Fleece).
The Nereids symbolized everything that is beautiful and kind about the sea. Their melodious voices sang as they danced around their father. They are represented as beautiful women, crowned with branches of red coral and dressed in white silk robes trimmed with gold. These nymphs are particularly associated with the Aegean Sea, where they dwelt with their father Nereus in the depths within a golden palace.