cerberus

Kerveros was son of Tyfon and Echidna and the dog of Hades. Plouton put him in front of the gates of Hades as guardian in order not to leave the dead to come out. He was a very wild beast and he had three heads or according to others fifty or one hundred. For hairs he had snakes and his tail was a tail of dragon with a head at the end. His voice was terrific and analogous to his appearance and that's why Hesiodus describe his voice as “chalcophonous” (=with copper voice).