Fear Liath also known as Big Grey Man or The Grey Man of Ben MacDhui is a seemingly malevolent type of mountain-spirit found in Scottish folklore, especially those surrounding the summit of Ben Macdui (the second highest mountain in Scotland) - similar creatures are found across several legends and are believed to both represent the cold, isolate and dangerous conditions of mountains (especially in early days of exploration) as well as being the result of optical illusions and paranoia.
Fear Liaths are also considered a kind of Bigfoot-like creature due to the fact they manifest at times as large hairy humanoids, they tend to be far more ghostly than most modern takes on Sasquatch however and are always associated with extreme feelings of terror and unease whenever they manifest, though they never harm humans directly.