This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Peryton (Medieval folklore)
The peryton is a mythological hybrid animal combining the physical features of a stag and a bird. The peryton lived in Atlantis until an earthquake destroyed the civilization and the creatures escaped by flight. A peryton casts the shadow of a man until it kills one during its lifetime, at which time it starts to cast its own shadow.
The peryton is said to have the head, neck, forelegs and antlers of a stag, combined with the plumage, wings and hindquarters of a large bird, although some interpretations portray the peryton as a deer in all but coloration and bird's wings.