I thought I'd pluck a little information about the negative transformation of earlier gods and goddesses by christianity, and did a search that brought me to a page that, at the very top, refers to the philosopher Joseph Campbell as "New Age ideologist Joseph Campbell." Just as the religion itself defines those that came before in lesser or pejorative terms, it appears they do so with their harshest critics. "New Age" my ass! He's as solidly Modernist as they come.   :)

Another site gave a better definition, and while his definition denotes the transformation, he doesn't use a demarkation to show that the transformation came about when christianity got it's hands on these creatures. I'll leave you with this definition and the perfect segue to the next bit of BS on this thread, quite possibly authored by Rapaire:

Harpy
            
Originally wind spirits, the Harpies' inital role is to carry to Hades the souls of the dead. The harpies are born from Typhon and Echinda. There are four Harpies: Aello (meaning rain-squall), Celaeno (storm-dark), Okypete (swift-flying), and Podarge (swift-foot). In later myths the Harpies are featured as winged monsters with pale female human faces with long hair and claws made of brass. Although invulnerable, they always look hungry and withered. Everything that they touch immediately becomes contaminated with an awful stench. They were afraid of only one thing: the sound of a brass instrument.