The Fuath are a malevolent class of fairy / water-demon found in Celtic mythology, the name "Fuath" translates roughly into "hate" and shows the creatures malicious nature.

Envisioned as shaggy monsters with webbed toes, spiked tails and no nose but like many fairies they could shape-shift and had regional variations : they liked to wear green clothing (usually robes), as this was considered the color of fairies in Celtic folklore.

They feared sunlight and cold iron (similar to trolls) and despite their evil nature could breed with humans : producing young that also had tails and webbed toes.

As far as personality goes the Fuath are often considered either a "cousin" or alternate guise of the more infamous Kelpie.