This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Cerberus (Greek)
In Greek mythology, Cerberus, often referred to as the hound of Hades, is a multi-headed dog that guards the gates of the Underworld to prevent the dead from leaving. He was the offspring of the monsters Echidna and Typhon, and was usually described as having three heads, a serpent for a tail, and snakes protruding from his body. Cerberus is primarily known for his capture by Heracles, the last of Heracles' twelve labours.
Descriptions of Cerberus vary, including the number of his heads. Cerberus was usually three-headed, though not always. Cerberus had several multi-headed relatives. His father was the multi snake-footed Typhon, and Cerberus was the brother of three other multi-headed monsters, the multi-snake-headed Lernaean Hydra; Orthrus, the two-headed dog that guarded the Cattle of Geryon; and the Chimera, who had three heads.