Nymph

Nymphs are nyxborn elemental nature spirits created by the Gods to protect the natural world. They represent all aspects of the wild, the land, and the sea, and as such their race is as varied as the elements they signify. Some are more powerful than others, but all are a force to be reckoned with when angered.
Divine servants that inhabit unspoiled corners of the world, nymphs protect places of natural power and infuse their surroundings with the magic of Nyx. Some are benevolent and aid those who live off the land, while others embody violent aspects of nature. In either case, nymphs generally avoid other sapient creatures, preferring to mind the cycles of nature, the daily interplay of wild animals, or other cosmic forces.
Occasionally though, groups of the same kind of nymphs congregate in a place of natural power or beauty. In times of special need, deities tied to facets of nature might employ nymphs as messengers, guardians of scouts.
The nymphs of Theros include the following mysterious beings:
Note: Still working on balancing these subraces. I'm aware they're a little OP atm so bear that in mind if you're considering playing a nymph using these stats/abilities.

Subraces

Alseid

Radiant Resistance: You have resistance to radiant damage.
Unearthly Beauty: Once per long rest you may add your charisma modifier to your AC.
Radiant Soul: You know the light cantrip. At 3rd level, you can cast bless at 2nd-level once per long rest. At 5th level, you can cast aura of vitality once per long rest. Charisma is your spellcasting ability for these.

Dryad

Speak with beasts & plants: You can communicate with beasts and plants as if you share a language.
Tree Stride: You may use 10ft of your movement to step magically into one living tree within reach and emerge from a second living tree within 60ft of the first, appearing in an unoccupied space within 5ft of the second tree. Both trees must be large or bigger in size.
One with nature: You know the druidcraft cantrip. At 3rd level, you can cast barkskin at 2nd-level once per long rest. At 5th level, you can cast plant growth once per long rest. Charisma is your spellcasting ability for these.

Lampad

Death-touched: You have resistance to necrotic and poison damage and you have advantage on saving throws against being poisoned.
Corpse Stride: You may use 10ft of your movement to step magically into one creature's corpse within reach and emerge from a second corpse within 60ft of the first (appearing in an unoccupied space within 5ft). Both corpses must be medium or bigger in size.
Born to Die: You know the chill touch cantrip. At 3rd level, you can cast gentle repose at 2nd-level once per long rest. At 5th level, you can cast life transference once per long rest. Charisma is your spellcasting ability for these.

Naiad

Invisible in water: The naiad is invisible while fully immersed in water.
Amphibious: You can breathe air and water.
Cold Resistance: The naiad is resistant to cold damage.
Ocean born: You know the shape water cantrip. At 3rd level, you can cast create or destroy water at 2nd-level once per long rest. Charisma is your spellcasting ability for these.

Oread

Flame-born: The oread is resistant to fire damage.
Infernal Legacy: You know the thaumaturgy cantrip. At 3rd level, you can cast hellish rebuke at 2nd-level once per long rest. Charisma is your spellcasting ability for these.

Nymph Traits

Ability Score Increase: CHA +2

Age: Nymphs reach maturity about 5 and live up to 500 yrs

Size: Medium - 4-6ft

Speed: 30ft

Languages: Common and Sylvan

Proficiencies: Perception, Deception

Fey: Your creature type is fey