Mythology Three Headed Dog. Hound of hades, three headed dog. In the greek mythical tradition, cerberus is the guardian of the gates of the underworld, the realm of hades.

Today, many people refer to the ancient greek deity kerberos by his roman name, cerberus, so we will too. Polycephaly is the condition of having more than one head.the term is derived from the greek stems poly (greek: Three headed dog guarding the entrance to hades.