black dog: black dogs can be si, ghosts, malevolent entities, phantoms, demons, shape-changers, etc. There are types of si that take the form of a black dog and the grim (usually a dog form) is often black as well. The lethal fairy barghest is a type of black dog with great infamy.
Most black dogs are not so deadly, and often haunt lonely and/or deserted places, seemingly content to frighten away intruders. Most are incorporeal, at least part of the time. The exceptions are more the norm, and run the gambit; some are helpful, benevolent, righteous (grim); others alien and terrifying, some are deadly.
Many black dogs are more or less harmless; some can be deadly if touched or spoken to; some black dogs are attached to a geographical area, others are rovers; some like the barghest are particularly perilous - these most often are attached to a geographical area (like a redcap), and haunt the loneliest and most forlorn areas of their territory, attacking and slaying lone travelers or their horses; other black dogs (of the deadly varieties) will enter a settlement in the dead of night, particularly during storms, and kill the unwary. These are usually si but some ghosts manifest as black dogs and behave in a similar, if not identical, manner. Most black dogs are content, however, to remain frightening, silent haunters of lonely passes and woods; black dog si are easily confused with ghosts and malevolent entities, and vice versa. It often is impossible without divination to determine the truth, though there are usually clues if a black dog is observed for a length of time. That can be a daunting – if not lethal – proposition, particularly in the case of the barghest, bogeys in black dog form, and killer ghosts that appear as black dogs.
