The Glaistig was a solitary supernatural being of the Scottish Highlands, with the upper half of a woman and the lower half of a goat, although she was also believed to appear in human and animal form. Her skin was grey, and long golden hair fell about her body. Like many of the fairy races she was often seen clothed in green, in the form of a long flowing robe, which covered her goat half.

She frequented the lonely lochs and rivers in the Highlands of Scotland, and is sometimes describes as a half earth, half water sprite, although in Gaelic her name means literally 'water imp'.

Like many supernatural being she could be both benevolent and malevolent depending on the story and had vampiric tendencies towards men, seducing them and drinking their blood, she was also said to be a trickster who enjoyed leading travellers astray and committing acts of mischief akin to a goblin (such as pelting people with stones) - however she was said to be kind towards children and shepherds.