The harpies are classical Greek monsters. There are three of them, appearing in various epics and even in some more modern texts, such as Neil Gaiman’s Sandman series. In most stories, the harpies are vicious, ugly creatures with the faces of old, ugly women and sharp talons.
It’s not an accident that their name means “snatchers.” Their position in the order of things was, generally, to be the carriers of any men or creatures wanted by the gods, and especially of wrongdoers to the Furies.
The Harpies are directly connected to the Furies—so much so that they are often conceived of as the same entities in different forms. In Roman, they are the Dirae. And they are powerful.
In the earliest stories, the harpies are beautiful women with large wings. The legend of Jason and the Argonauts, though, depicts the harpies as foul birds with the faces of ugly women, leaving an awful stench as they came to punish King Phineus by snathing the food from his table.
The harpies became synonymous with ugliness, and Dante has them populate the tortured wood in the 7th ring of Hell. By the 1600s, harpy was in use as a synonym for an annoying, bossy woman. Though the term isn’t as commonly used now, it’s still one that means an ugly or irritating woman.
Perhaps the power of the harpies is one of the reasons that their descriptions changed. If they were not only incredibly powerful but incredibly beautiful, they were much more dangerous. Better if they were only either very powerful or very beautiful. Whatever the reason, that ugliness and shrewish personality have been the predominant concepts associated with the harpy.