According to Greek mythology Echidna was the nasty bitch who whelped Cerberus. A dastardly damsel who sported the head and torso of a human woman with bewitching dark eyes, the other half serpent. The bitch lured men to her cave and devoured them. Dear, dear.
And his outrageous Pater breathed fire from a hundred heads, dabbed with glowing red eyes and flew on a hundred wings. The dragon Typhon was feared by all, even the other gods on Mount Olympus. He existed exclusively to spread fear and destruction.
Their heinous offspring became a faithful servant to Hades and guardian of the underworld. Patrolling the banks of the River Styx, boundary between the living and the dead, Cerberus made sure that no living soul entered Hades without permission. He watched zealously over the spirits and would savagely devour any who tried to escape back to the land of the living.