In fact, this dog a mythological figure in Irish, Scottish, and British folklore. Dogs are variously presented as friends to humans, supernatural entities, or even dark, menacing creatures. Great Britain is rife with tales of phantom black dogs. Nearly every county has at least one example of such a beast. This spectral creature, usually shaggy and as big as a calf, was familiar throughout the insular Celtic world as an indication of great change and probable death. Occasionally Black Dogs could be helpful, but it was necessary to be wary of them, for one glance of their eyes could kill.
In Westmoreland the dog was called the Capelthwaite and performed doggy services, like rounding up herds, for the locals, while the same creature on the Isle of Man was called the Mauthe Doog. The Black Dog is also familiar to Irish folklore and has been sighted at Irish sacred sites as recently as the 1990s. It is likely that lore about this ghostly creature inspired Sir Arthur Conan Doyle’s “The Hound of the Baskervilles.”