Peryton
Perytons are mythical monsters resembling giant eagles with the heads of stags, who cast human shadows and eat human hearts... no, we're not making this shit up. Like many other crazy mythical monsters, they've shown up in Dungeons & Dragons, but have also made appearances in the Monsters and Animals supplement for the Palladium Fantasy Role-Playing Game.
Interesting fact: The Peryton isn't actually from mythology. It was actually made up as a joke to show how easy it is to make up a monster that sounds like it could be from mythology but isn't.
Further Reading
You can find an exhaustive discussion of the Peryton's history in D&D, including naming all sourcebooks that refer to it, over here: http://www.enworld.org/forum/content.php?4552-Monster-ENCyclopedia-Peryton
Gallery
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1e
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AD&D Monster Card
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2e
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3e