Hell-hounds

The hell-hound is a creature of mystery, death, and more. It is found all over Europe, particularly the British Isles and northern Europe. However, it is most remembered for its role in Greek mythology. They were said to live in the Underworld, also known as Hades. They guard the exits, and the dead. Perhaps the most famous hell-hound is Cerberus, the three-headed giant that guarded the entrance to the land of the dead.
The hell-hound is always black in colour, with its fur like the night. Indeed, that is where it spends most of its time. Various tales tell of different numbers of heads. The most common is one, and yet there are others, such as Cerberus, who have three, or even more. The hell-hound will have red eyes, that glow with malice. A foul stench also surrounds the beast, warning those ahead of their impending doom. They are also very strong. Speed is another attribute to which few can match it, as they are said to be able to outrun wild stallions and lift one too, with its jaws.
In nearly all cultures that mention the hell-hound it has been associated with death and the afterlife. Early Christianity claimed it was the beast that guarded the gates to hell, and Greek mythology stated they guarded the dead spirits in Hades. They also have a strong association with fire. Eyes are said to be the window to one's soul, and if that were true, it would certainly fit with the hell-hound. A soul of deadly fire is reflected in the burning orbs called eyes, ever-flickering in the black night.
It is this ever-looming presence of death that has led to one particularly gruesome legend. It is said that were you to catch sight of a hell-hound three times or more, your death was imminent, and very soon. It is also said that if you were to hear or see its howl, your death was nigh. They often wander graveyards, and thus it was sometimes said they would only howl in such a place.
Despite their preferences for places of death, the hell-hounds were also seen wandering ordinary streets. You may have come home late from a party, and be on your way home. Suddenly, the air turns cold, and you feel a looming presence. Red lights appear from nowhere, and a dark shape moves. You scream, and watch as a giant beast runs away. It does not run in fear, rather, it has warned you, death is everywhere.

• http://en.wikipedia.org/wiki/Hellhound
• http://powerlisting.wikia.com/wiki/Hellhound_Physiology
• http://tfwalsh.wordpress.com/2011/08/08/hellhound-hells-guard/
• http://www.mythicalcreaturesguide.com/page/Hell+Hound#fbid=aD2b-95Gn_l