The Phantom Hound was the disguise of an ordinary Irish wolfhound, painted to glow in the dark.
It looked like a ghostly glowing green dog.
Although the Hound sometimes growled and bayed, Velma Dinkley discovered that he was actually friendly and only chased people because he wanted to play.
Scooby-Doo (DC Comics)
Edward Darkmoor created the illusion of the Phantom Hound, a legendary curse in his family that meant the family line was coming to an end. The household was running out of money because nobody had discovered the treasure map that the former Lord Darkmoor wrote on the back of the will. Edward thought the Hound would frighten his brother into selling. When the gang helped discover the treasure, Edward confessed and all was forgiven.