I sprang to my feet, my inert hand grasping my pistol, my mind paralysed by the dreadful shape which sprung out upon us from the shadows of the fog.

A hound it was, an enormous coal-black hound, but not such a hound as mortal eyes have ever seen. Fire burst from its open mouth, its eyes glowed with a smouldering glare, its muzzle and hackles and dewlap were outlined in flickering flame. Never in the delirious dream of a disordered brain could anything more savage, more appalling, more hellish, be conceived than that dark form and savage face which broke upon us out of the wall of fog.

.

Description of the Hound of Dartmoor as recorded by Doctor Watson in The Hound of the Baskervilles by Sir Arthur Conan Doyle.

. . .