Cerebus the Myth - the dog
According to Greek legend Cerberus was a three-headed dog that guarded the entrance to the underworld. He was rather vicious and guarded Hades passionately. He was often called by the common people "the hound of Hades". Cerberus was also the subject of one of the tweleve labors of Hercules. He was to bring the poor hound from his home in the underworld to Eurystheus. He succeded with the blessing of Hades by mastering the hound in a fight using no weapons and instead merely throwing his arms around of Cerberus's three heads and wrestling him to the ground.
Interestingly enough there are conficting stories of what Cerberus actually looked like. Some say that he was a Titan-sized hound with fifty heads while others claim he had merely three heads the tail of a dragon and the hair of a Gorgon covering his heads. What is never contested is the hound's taste for raw flesh.