Nymphs, Naiads, and Nereids

Nymph

Medium fey, any alignment

Armor Class 12 (unarmored)

Hit Points 33 (6d8 + 6)

Speed 40 ft

STR 11(+0)

DEX 14 (+2)

CON 12 (+1)

INT 10 (+0)

WIS 13 (+1)

CHA 14 (+2)

Skills Deception +4, Persuassion +4, Religion +2

Senses passive Perception 10

Languages Ancient Greek, Animal Speak

Challenge 2 (450 XP)

Spellcasting: A nymph is a 4th-level spellcaster, its spellcasting ability is Charisma (spell save DC 12, +4 to hit with spell attacks.) Although it varies based on the type of nymph, the average nymph has the following spells prepared: 

Cantrips (at will): light, sacred flame, druidcraft
1st level (4 slots): animal friendship, cure wounds, shield of faith
2nd level (3 slots): enthrall, lesser restoration

Actions

Bronze Dagger. melee or ranged weapon attack: +4 to hit, reach 5 ft. or range 20/60 ft., one creature. Hit: 4 (1d4 +2) piercing damage.

Nymphs are the personification of the creative qualities in nature. They are often the daughters of Titans or Olympians and can be found throughout Greece in the secret places of the wild. They are beautiful nubile maidens who live in the forests, rivers, and mountains. According to german mythology scholar Walter Burkert: "The idea that rivers are gods and springs divine nymphs is deeply rooted not only in poetry but in belief and ritual; the worship of these deities is limited only by the fact that they are inseparably identified with a specific locality."

There are many different nymphs, their variety is based upon the nature they represent. When it comes to their stats as creatures, they are all roughly the same. They differ when it comes to the spells they prepare, which reflect their nature.

Hylas and the Water Nymphs by Henrietta Rae

Hesperides, Nymphs of the Evening
The Hesperides were daughters of Atlas and nymphs of the evening and sunset. They tend the garden in which the golden apples are stored in Tartessos, a region past the Pillars of Heracles on the Iberia Peninsula. There are three of them: Aigle ("Dazzling Light"), Erytheia, and Hesperethusa ("Sunset Glow"). They reflect the color of the setting sun: red, yellow, and gold. They have the following spells prepared:

Cantrips (at will): light, dancing lights, druidcraft
1st level (4 slots): faerie fire, cure wounds, sleep
2nd level (3 slots): enthrall, moonbeam

Naiads, Nymphs of Fresh Water

Distinct from river gods who embody rivers, Naiads inhabit the still waters of marshes, ponds, and lakes. Naiads can be dangerous, they are known to kidnap beautiful mortals or become wildly jealous. For example, when the shepherd Daphnis was unfaithful to his naiad lover Nomia she permanently blinded him. 

Cantrips (at will): frostbite*, shape water, vicious mockery

1st level (4 slots): create water, fog cloud, hex

2nd level (3 slots): blindness/deafness, misty step, prayer of healing

Oreads, Nymphs of the Mountains

The Oreads are nymphs of the countless rocky mountains that make up the Greek landscape. They are given specific titles based on where they dwell. The Idaeae hail from Mount Ida, and the Nomia from Mount Nomia. Oreads often joined Artems while she hunted since most forests were located on the slopes of rugged hills and mountains. The forests in the lowlands had been cleared for farming. They are connected with the connifers that grow in the mountains. 

Cantrips (at will): druidcraft, mold earth*, magic stone*

1st level (4 slots):  entangle, speak with animals, hail of thorns

2nd level (3 slots): barkskin, earthbind*, spike growth

Hylas and the Nymphs by John William Waterhouse

Dryads, Nymphs of the Forests

The forest spirit Oxylos had several dryad daughters who presided over specific types of trees: Aegeiros was the nymph of the black polar, Ampelos was the nymph of the wild grape vine, Balanis was the nymph of oak-trees, Karya was the nymph of hazelnut and walnut trees, Kraneia was the nymph of the cherry tree, Morea the nymph of the mulberry tree, Ptelea was the nymph of the elm tree, and Syke was the nymph of the fig tree. There are probably as many different dryads as there are species of tree in Greece. 

Cantrips (at will): druidcraft, shillelagh, thorn whip

1st level (4 slots): entangle, goodberry, snare*

2nd level (3 slots): barkskin, enlarge/reduce, pass without trace, 

Nereids, Nymphs of the Mediterranean Sea and Oceanids, Nymphs of the Ocean

Nereids and Oceanids are essentially the same, in that they are nymphs of bodies of saltwater. The Nereids were the fifty daughters of Nereus and Doris and would often accompany Poseidon. Amphitrite was a Nereid who was the consort of Poseidon.They were friendly and helpful to sailors. Meanwhile, the Oceanids were the three thousand daughters of Oceanus and Tethys. They also had three thousand sons called the Potamoi, the gods of rivers and streams. (Which is an article all of its own). 

Cantrips (at will): gust, shape water, thunderclap

1st level (4 slots): create/destroy water, thunderwave, zephyr strike

2nd level (3 slots): gust of wind, levitate, enthrall

*Found in Xanathar's Guide to Everything

Design Notes
I wanted to take a moment to talk about the decisions behind this creature. Obviously, in 3rd edition there was a nymph or in Pathfinder. But I wanted to create a nymph that was more reflective of Greek mythology. In the Heroic Age campaign setting, magic users are rare. If a hero approaches a priest at a temple, most of the priests are going to be 1st level clerics, and the high priest is going to be a 2nd level cleric. They are not going to be very powerful spellcasters. Meanwhile, many nymphs are children of gods. It is only natural that they are more powerful. I was looking for a CR 2 divine spellcaster in creating this Nymph.

They are not meant to be monsters in the traditional sense, it is unlikely the players are going to roll up on some nymphs and kill them. However, they may want to kidnap some or steal from them. The nymphs were given spells that were either thematic, or designed to help them escape from satyrs trying to take advantage of them.