Hellhounds are the devolved forms of demons. They are created by a stronger demon forcing the unfortunate through a transformation that alters their mind, and eventually their body, into the charred and savage form of a hellhound. Hellhounds are typically controlled psychically by other demons and used to track down and capture souls bound for hell. On earth, their senses are very poor and they are almost blind, so hunt by sound and smell. Once a hellhound has tasted the blood of a person, they are able to track them anywhere on the planet. They cannot be stopped or deterred unless they are killed or given a new target. Holy iron will wound them, but the only certain way to kill a hellhound is to drown it in salt water.
C. A. Harland 