Cerberus
the three-headed dog which guards the entrance of the king dom of Hades and Persephone .
Orpheus, when he descended into the infernal regions in search of Eurydice, lulled him to sleep with his lyre; and Hercules dragged him from the gate of Hades, when he went to redeem Alceste.
The fellow-monster of Cerberus was Orthros. The names of these dogs appear in the Vedic poems under the forms of Sarvara and Vritra, the two dogs of Yama.