Neo-Odyssey-Harpy Picture

The harpies were sisters of Iris, daughters of Thaumas and Electra.

Phineas, a king of Thrace, had the gift of prophecy. Zeus, angry that Phineas revealed too much, punished him by blinding him and putting him on an island with a buffet of food which he could never eat. The harpies always arrived and stole the food out of his hands before he could satisfy his hunger, and befouled the remains of his food. This continued until the arrival of Jason and the Argonauts. The Boreads, sons of Boreas, the North Wind, who also could fly, succeeded in driving off the harpies, but without killing any of them, following a request from Iris, who promised that Phineas would not be bothered by the harpies again, and "the dogs of great Zeus" returned to their "cave in Minoan Crete". Thankful for their help, Phineas told the Argonauts how to pass the Symplegades.

In this form they were agents of punishment who abducted people and tortured them on their way to Tartarus. They were vicious, cruel and violent. They lived on Strophades. They were usually seen as the personifications of the destructive nature of wind. The harpies in this tradition, now thought of as three sisters instead of the original two, were: Aello ("storm swift"), Celaeno ("the dark") — also known as Podarge ("fleet-foot") — and Ocypete ("the swift wing").

Aeneas encountered harpies on the Strophades as they repeatedly made off with the feast the Trojans were setting. Celaeno cursed them, saying the Trojans will be so hungry they will eat their tables before they reach the end of their journey. The Trojans fled in fear.
Harpies in the infernal wood, from Inferno XIII, by Gustave Doré, 1861

Harpies remained vivid in the Middle Ages. In his Inferno, XIII, Dante envisages the tortured wood infested with harpies, where the suicides have their punishment in the second ring:
I am Zeus
nyx
Neo-Odyssey-Harpy
Sonorare
Coronis and the Crow