The Oresteia is a trilogy of Greek tragedies written by Aeschylus that tells the story of the House of Atreus, focusing on themes of justice, vengeance, and the evolution of societal laws. The three plays – Agamemnon, The Libation Bearers, and The Eumenides – trace the cycle of revenge within a family and culminate in the establishment of a court system, reflecting the shift from personal retribution to institutional justice.