The Guardian Cerberus                                

Greek legend claims that the Cerberus was a three-headed dog, with snakes for a mane and another viper for a tail.  His three heads were said to represent the past, the present and the future.  Cerberus guarded the gates of Hades to prevent the living from entering the underworld and those imprisoned there from leaving it.  If Cerberus was exposed to sunlight, he barked and where his saliva fell, a poisonous plant grew.  He was outwitted by Orpheus who charmed him into a deep sleep by playing his lyre and he was then able to enter and escape the underworld at will.