Fuath

A Fuath (pronounced foo-ah) (Fuathan pl.) is an evil, Gaelic water spirit.

Its name is sometimes used as a regional variance for Kelpie or Uisges in Northern Ireland or the Bean-Nighe. The Scottish use the name to refer to generic water spirits who inhabit the sea, rivers, fresh water, or sea loches. Sometimes, this name is even given to highland or nature spirits, but all forms with the name are evil.

Their appearance ranges from covered in shaggy, yellow fur to just having a mane down its back, webbed toes, tails with spikes, and no nose. They are prone to wearing green, whether it be a dress, robe, or kirtle, as it is the color of faeries.

They sometimes intermarry with humans (typically the female), whose offspring will share a mane, tail, and/or webbed digits. Their banes include sunlight and cold steel, which will kill them instantly. They grow restless upon crossing a stream.

An alternative name for this class of monsters is Arrachd.

Reference

1.Rose, Carol. (2000). Giants, Monsters and Dragons. Norton