Black Dog is the name given to a being found primarily in the folklores 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.
Stories tell of them terrifying their victims, but leaving them alone to continue living normal lives; in some cases it has supposedly happened before close relatives to the observer die or become ill.
In other tales the animal is regarded as relatively benign and said to accompany women on their way home. Some black dogs have been said to help lost travellers find their way home through the moors and are more often helpful than threatening.