"there came a glare of red light out of his eyes"
Hell hound
Creative Commons Attribution Share AlikeHell hound - Credit: VenomD95
This fetching stained glass window shows the devil with red eyes
GNU Free Documentation LicenseThis fetching stained glass window shows the devil with red eyes - Credit: Ecelan

A well-known attribute of the devil: he has been portrayed as a red-eyed demon in Christian art since the eleventh century. Folklore commonly gives him this characteristic in his manifestation as a phantom black dog, a fearsome being that guards the mouth of hell. Interestingly, this was one of his favorite guises for visiting witches, and their animal familiars are often identified as black dogs, too.