The Erinyes were three female goddesses, seeking vengeance against anyone who had sworn a false oath or had done an evil act. Their Roman equivalents were the Furies or Dirae. They were created when the Titan Uranus was castrated by his son Cronus and his genitals were thrown into the sea; the drops of blood that fell onto Gaia (the earth) created the Erinyes and the Meliae, while out of the sea foam, Aphrodite emerged.
The number of the Erinyes is unknown and is very variable; however, three are the best known; Alecto (the unceasing), Megaera (the grudging) and Tisiphone (the vengeful destruction). The role of the Erinyes was to tantalise anyone who committed crimes, or hubris (insolence against the gods).
One of the best known literary examples in which the Erinyes had a major role is Aeschylus' trilogy Oresteia; in it, Orestis, the son of Agamemnon and Clytemnestra, slays his mother who had killed her husband for sacrificing their daughter Ifigeneia. Committing such a grave crime as matricide, Orestis is tormented by the Erinyes and seeks help at the Oracle of Delphi; there, he is told to go to Athens and ask goddess Athena for a trial. In the trial, the Erinyes appear as accusers of Orestis, saying that more blood must be spilled. The jury votes are evenly split and Athena decides to acquit Orestis. The Erinyes threaten to torment all Athenians from now on; but Athena, using a mixture of bribery and threats, changes their minds. Instead, the Erinyes become the Semnai (venerable ones) and instead of vengeance, they become the protectors of justice.