Harpy mythology:

The most celebrated story in which the harpies play a part is that of King Phineus of Thrace, who was given the gift of prophecy by Zeus. Angry that Phineus gave away the god's secret plan, Zeus punished him by blinding him and putting him on an island with a buffet of food which he could never eat because the harpies always arrived to steal the food out of his hands before he could satisfy his hunger. Later writers add that they either devoured the food themselves, or that they dirtied it by dropping upon it some stinking substance, so as to render it unfit to be eaten.

This continued until the arrival of Jason and the Argonauts. Phineus promised to instruct them respecting the course they had to take, if they would deliver him from the harpies. The Boreads, sons of Boreas, the North Wind, who also could fly, succeeded in driving off the harpies. According to an ancient oracle, the harpies were to perish by the hands of the Boreades, but the Boreades were to die if they could not overtake the harpies. The harpies fled, but one fell into the river Tigris, which was hence called Harpys, and the other reached the Echinades, and as she never returned, the islands were called Strophades. But being worn out with fatigue, she fell down simultaneously with her pursuer; and, as they promised no further to molest Phineus, the two harpies were not deprived of their lives. According to others, the Boreades were on the point of killing the harpies, when Iris or Hermes appeared and commanded the conquerors to set them free, promising that Phineus would not be bothered by the harpies again. "The dogs of great Zeus" then returned to their "cave in Minoan Crete". Other accounts said that both the harpies as well as the Boreades died. Thankful for their help, Phineus told the Argonauts how to pass the Symplegades.

Tzetzes explained the origin of the myth pertaining to Phineus, the harpies, and the Boreades in his account. In this late version of the myth it was said that Phineus, due to his old age, became blind, and he has two daughters named Eraseia and Harpyreia. These maidens lived a very libertine and lazy life, abandoning themselves to poverty and fatal famine. Then Zetes and Calais snatched them away somehow, and they disappeared from those places ever since. From this account all myths about them [i.e., the harpies] started, as was also retold by Apollonius in his own story of the Argonauts.

Aeneid

Aeneas encountered harpies on the Strophades as they repeatedly made off with the feast the Trojans were setting. Celaeno utters a prophecy: the Trojans will be so hungry they will eat their tables before they reach the end of their journey. The Trojans fled in fear.

Harpy origin lore:

The Harpies live throughout in various parts of the world in hiding from humans to live out their lives in peace. However, there are a small group who live within the Castle of the Dark Master who thrive on hunting and devouring humans.

These Harpies are another set of foot soldiers who go into battle on rare occasions. They are difficult to kill as their skin is insanely tough and their speed is faster than the human eye can see.

If however they are killed, the surviving bird women will hunt for human males and force them to mate in order to birth more Harpies to replace their fallen sisters. The babies then devour the human father once they hatch.

Like many, there is an alpha amongst them and she makes all the decisions for her clan. Only the master of the Castle has higher authority over the alpha Harpy.

Here's the original version of the Harpy (Harpies).