Puca

A black horse with fiery eyes appears alone at night in Ireland, offering wild, terrifying rides to anyone bold enough to mount it. This shapeshifting spirit constantly changes form, goat, cat, hare, and has a fixed date on the Celtic calendar: after November first, every uncollected wild fruit belongs only to it, and it spoils them on purpose, as if claiming what's rightfully his.

An ambivalent fairy being that shifts shape — chiefly a black horse with fiery eyes, but also a goat, cat, hare, or man — and may bring fortune or ruin. The púca-horse offers wild, terrifying rides to whoever mounts it.

Within the folk and mythological corpus compiled by the Codex Monstrorum, the creature Puca occupies a distinctive role in the symbolic imagination of its culture of origin. Its mythos articulates primal human anxieties, the mystery of untamed wilderness, and social norms preserved through the lens of bestiary literature.

It is tied to Samhain (1 November): after that date, uncollected wild fruit belongs to the púca, who 'spoils' it (púca's spit). It can speak and give counsel, and even render farm services if well treated, in the ambivalent pattern of Celtic spirits.

The púca was respected by leaving it a share of the harvest and not picking fruit after Samhain; those who treated it courteously might receive prophecies. Mounting it without leave guaranteed a hellish ride over fields and cliffs.

First appearance and primary records: A shapeshifting spirit of Irish folklore (púca; kin to the English Puck and the Welsh pwca), attested in Celtic tradition and gathered by folklorists such as Lady Wilde and W. B. Yeats in the 19th century.

Oral transmissions and preserved manuscripts indicate that legends surrounding Puca underwent substantive evolution over successive centuries. From archaic oral traditions to classical and medieval written records, each period reframed the creature according to its own ethical and cosmological paradigms.

An unstable form: most commonly a sleek black horse with flaming eyes and a wild mane; also a horned goat, a large cat, a hare, an eagle, or a hairy man. Shapeshifting is its essential trait.

It regulates the harvest and respect for seasonal cycles (Samhain) and personifies the ambivalence of the supernatural — blessing or punishment according to conduct. It binds the year's boundary, the land, and the Otherworld.

Like the kelpie and the each-uisge, it embodies the water/night-horse that carries off the rider; yet the púca stands out for its total mutability and ambivalence — it can help as readily as harm.

Alive in Irish folklore, literature (from Yeats to the famous play/film Harvey, where the pooka is an invisible rabbit), and pop culture; it is one of the best-known Celtic fairy spirits, an emblem of the Otherworld's ambivalence.