Harpy

Harpies are creatures native to Theros that resemble a hybrid of human and bird. They typically have humanoid faces and torsos with the legs and wings of a bird.
Across all their sub-types, harpies are natural scavengers and avid collectors, hoarding all manner of trinkets and baubles which they trade amongst each other as currency. The few harpies who make homes in civilisation are usually merchants and collectors of rare and unusual items.
The physical and behavioural characteristics of harpies vary widely but most can be categorised as one of the following:

Hunter Harpies

Hunter Harpies are the largest of the harpy sub-types, resembling birds of prey in the colouring and patterns of their feathers.
Culturally, hunter harpies are a nomadic and matriarchal people, travelling widely across mountainous desert regions such as the Phoberosi Badlands in search of food and treasure - though what harpies consider to be 'treasure' often differs from civilised society.
Due to their relative weakness and the scarcity of food in these regions, Harpies are known for feasting on the rotting flesh of corpses (usually travellers who have fallen victim to roaming minotaur bandits) As such, hunter harpies rarely kill their prey directly, preferring to trick or lead creatures into dangerous territory where they will be picked off by other more dangerous monsters or by the harsh environment.
Widely considered dangerous or troublesome pests, most harpies avoid straying too close to civilisation but those who do cause havoc by stealing and eating livestock.

Society and Culture

Hunter Harpy society is divided into various tribes, each with their own unique laws, culture and history. With a couple of notable exceptions, these tribes are led by female chieftains revered for their strength, intelligence, wealth or beauty (different tribes consider each of these of varying importance) Chieftains are usually identified by ornate headdresses resembling horns or antlers and layers of ornate jewellery.
Sexually, harpies have no concept of monogamy or sexual orientation, usually mating with several partners throughout their lifetime (typically from other tribes, to reduce inbreeding) but will commonly have life partners who act as companions and help to raise their children. While these relationships are sometimes sexual in nature, more commonly they are purely platonic familial bonds. Harpies consider their family to be those that raised them rather than those who share their blood.
Despite their cultural emphasis on self-sufficiency and independence, harpies strongly value family, fiercely defending those they consider parents, children, siblings or partners.
Hunter harpies usually build their nests atop the mountains of Velos and Vesios and migrate South in Winter.

Special Abilities

Hunter Harpies possess the following abilities:
Ability Score Increase: +2 constitution
Mountain Born: Resistance to Cold Damage
Blood Frenzy: Advantage on melee attacks against creatures with below half HP

Sea Harpies

Sea harpies, sometimes referred to as sirens, live and travel between the scattered islands across the Siren Sea. They are usually black, white and grey in colouring, resembling sea birds such as seagulls and albatrosses.
They are known for luring sailors to their deaths with their enchanting song, picking clean the wrecks of their ships and feeding on their corpses. However, more peaceful communities survive on fish and ocean plants, preferring to stay out of the way of potentially violent humanoids like humans, elves or tritons.

Society and Culture

Much rarer than their Hunter cousins, Sea Harpies tend to live in small, insular communities and contrary to the Hunters' nomadic lifestyle, Sea Harpies are highly territorial, viciously guarding the islands they call home. They live in close-knit communities which - like their hunter counterparts - are typically female-led. However, they typically rule in councils of three or four rather than uniting under a single leader.
In Sea Harpy Communities it is custom for female harpies to hunt and provide while males care for their offspring. As such, male harpies are rarely seen, typically dwelling in the heights of mountain cliffs or in hidden caves where their offspring will be relatively safe from predators and environmental hazards.
Reliant on the ocean's bounty and the wayward ships she steers towards them, most Sea Harpies are devout worshippers of Thassa, periodically sacrificing their most valuable treasures in exchange for her protection. In accordance with Thessa's values Sea Harpy societies value gradual change and encourage acceptance of where life's currents take them.
In addition to paying tribute to Thassa, Sea Harpies commonly honour and pay respect to Nylea who preserves their way of life and Keranos whose storms produce more wrecked ships for them to pick clean.

Special Abilities

Sea Harpies possess the following abilities:
Ability Score increase: +1 constitution, +1 charisma
Siren Song: You know the cantrip vicious mockery. At 3rd level you can cast charm person once. At 5th level you can cast enthral once. Spells cast using this trait are recovered after a short rest. Charisma is your spellcasting ability for these spells. 
Dark Devotion: Advantage on saving throws against being charmed or frightened

Pygmy Harpies

Easily identified by their tiny size, variety of colouring and and large, dark eyes, Pygmy harpies, sometimes referred to as Domestic Harpies, are small, herbivorous creatures who subsist on nuts, seeds and berries and keep mostly to themselves. They are beloved of Karametra and well regarded in her city of Setessa.
Outside of Setessa, they typically live in heavily forested areas far from civilisation, such as the Nessian Woods.

Society and Culture

Like Sea Harpies, pygmies possess a strong sense of community and group identity, banding together in times of struggle and promoting equality and fairness. Culturally they are diplomatic and non-confrontational, valuing patience and restraint.
Music and song are a key part of Pygmy Harpy culture.

Special Abilities

Pygmy Harpies possess the following abilities:
Ability Score increase: +2 wisdom
Soothing Song: At 1st level you can cast calm emotions once. At 3rd level you can cast sleep once. Spells cast using this trait are recovered after a short rest. Wisdom is your spellcasting ability for these spells. 
Naturally Stealthy: You can attempt to hide behind a creature at least one size larger than you.

Harpy Traits

Ability Score Increase: DEX +2

Age: Harpies reach maturity about 10 and typically live up to 60 yrs

Size: 4-5ft (Hunter or Sea Harpy), 2-3ft (Pygmy Harpy) Your size is medium.

Speed: 25ft (walking), 30ft (flying)

Languages: Common and Harpy

Talon Strike: Your talons are natural weapons which deal 1d4+DEX slashing damage.

Winged: You have a flying speed of 30ft. You cannot use this flying speed if wearing heavy armour or if encumbered.