Am Fear Liath Mòr (also known as the Big Grey Man of Ben MacDhui or simply the Greyman) is the name of a presence or creature which is said to haunt the summit and passes of Ben Macdui, the highest peak of the Cairngorms and the second highest peak in Scotland (also the British Isles). It has been described as an extremely tall figure covered with short hair, or as an unseen presence that causes uneasy feelings in people who climb the mountain. Evidence of the existence of this creature is limited to various sightings and a few photographs of unusual footprints. It was traditionally seen as a supernatural being, but Am Fear Liath Mòrhas been compared to the Yeti of the Himalaya and the Sasquatch orBigfoot of North America. References to wild 'Greymen' in Scotland and similar creatures elsewhere in Europe, sometimes called Wudewas or 'Wood Men', date back to the 13th century, and are believed by some to represent relict hominids.
In 1925, the noted climber John Norman Collie recounted a terrifying experience he had endured while alone near the summit of Ben MacDhui some 35 years before. "I began to think I heard something else than merely the noise of my own footsteps. For every few steps I took I heard a crunch, and then another crunch as if someone was walking after me but taking steps three or four times the length of my own." Collie was unable to make out the source of the noises because of mist, and continued "... [as] the eerie crunch, crunch, sounded behind me, I was seized with terror and took to my heels, staggering blindly among the boulders for four or five miles." Other climbers have also reported similar experiences, many describing uncontrollable feelings of fear and panic, some actually seeing a huge grey figure behind them, and others only hearing sounds or even succumbing to inexplicable feelings of terror while in the area.
In the Matt Lamy book 100 Strangest Unexplained Mysteries, Lamy notes a sighting in the early 1990s in which three men caught sight of a bipedal creature with an eerie, inhuman face in a forest near Aberdeen. Several weeks later, whilst driving through the area at night, the creature appeared again and ran alongside their car even at speeds of 45 miles per hour, seemingly trying to enter the vehicle.
Similar panic responses have been reported in many North American Sasquatch encounters, and explanations involvinginfrasound or pheromones have been advanced. Cryptozoologist Karl Shuker has expressed belief that the creature is the guardian of an inter-dimensional portal in his 1997 book, The Unexplained. However, hallucinations and panic brought on by isolation and exhaustion, or an optical illusion similar to the Brocken spectre, are very plausible explanations for the Big Grey Man legend. A Brocken spectre, or 'glory', can occur in certain atmospheric conditions when the sun is at a particular angle. The subject's shadow can be cast onto low lying clouds around them, creating the illusion of a large shadowy humanoid figure. This is the most commonly advanced theory to explain the reported sightings.