A black dog is the name given to an entity found primarily in the folklore of the British Isles. The black dog is essentially a nocturnal apparition, often said to be associated with the Devil or a hellhound. Its appearance was regarded as a portent of death. It is generally supposed to be larger than a normal dog, and often has large, glowing eyes. It is often associated with electrical storms (such as Black Shuck's appearance at Bungay, Suffolk), and also with crossroads, places of execution and ancient pathways.
The origins of the black dog are difficult to discern. It is impossible to ascertain whether the creature originated in the Celtic or Germanic elements in British culture. Throughout European mythology, dogs have been associated with death. Examples of this are the Cŵn Annwn,Garmr and Cerberus, all of whom were in some way guardians of the underworld. This association seems to be due to the scavenging habits of dogs. It is possible that the black dog is a survival of these beliefs. Black dogs are almost universally regarded as malevolent, and a few (such as the Barghest) are said to be directly harmful. Some, however, like the Gurt Dog in Somerset and the Black Dog of the Hanging Hills in Connecticut, are said to behave benevolently.