The Oresteia is a trilogy of Greek tragedies written by Aeschylus which concerns the end of the curse on the House of Atreus. When originally performed it was accompanied by Proteus, a satyr play that would have been performed following the trilogy; it has not survived. The term "Oresteia" originally probably referred to all four plays, but today is generally used to designate only the surviving trilogy. The only surviving example of a trilogy of ancient Greek plays, the Oresteia was originally performed at the Dionysia festival in Athens in 458 BC, where it won first prize. A principal theme of the trilogy is the shift from the practice of personal vendetta to a system of litigation. The name derives from the character Orestes, who sets out to avenge his father after his mother's affair with Aegisthus.