How are the "Furies" (avengers, the spiritual agents of vengeance) described in The Oresteia before the trial? What does this imply about the nature of vengeance?
In The Oresteia by Aeschylus the Erinyes or Furies are female chthonic deities. Three aged crones, they were born from the drops of blood that fell on the ground when Cronus castrated his father Uranus. They are responsible for revenge, and Aeschylus often uses the word "dike" (justice) and words with similar sounds when discussing them, as well as often referring to blood.
They represent the endless cycle of blood vengeance in which spilled blood calls for more blood to be spilled in retribution. Their nature as goddesses is harsh, patient, implacable, and unrelenting, absolutely devoted to their mission, and not easily propitiated by flattery, appeals to mercy, or bribery. They represent the notion of justice at its most raw, and are part of a primitive, pre-Olympian stage of Greek religion, a personification of the nature of vengeance more that fully individuated anthropomorphic deities such as Athena or Apollo.