This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Napaeae (Greek)
In Greek mythology, the Napaeae ("a wooded dell") were a type of shy but mirthful nymph. They lived in mountain valleys, glens or grottoes. They are associated with Artemis, and often accompany her. They are young maidens wearing graceful garments, long hair and a gold ring on their heads as they sing and dance.
Napaeae were nymphs of dells and Leimonides were nymphs of meadows. These very specific types of land nymphs were not widely attested to in the works of Greek writers and artists. There are no details as to how many there were and very few are named individually in myths.