Prometheus is one of the richest characters in Greek mythology. Before going through a summary of the play, understanding the play's rich mythological background is vital.
In early variations of the story, Prometheus is a trickster figure, like the coyote character in certain Native American folklore traditions. He outwits Zeus, king of the gods, on more than one occasion, usually as part of his efforts to help man. As time passed, Prometheus became more than a trickster. Myth and literature gave him an awesome place as visionary, genius, and suffering champion of mankind.
Prometheus was a titan, the race of old gods who reigned before Zeus and the Olympians. Prometheus, whose name means "Forethinker," was blessed with the gift of prophecy by his mother Themis, the primal earth goddess and ultimate mother of all. Prometheus initially tried to counsel Cronos, lord of the titans, in his strategies against Zeus and the new young gods. But he failed to convince Cronos of his plans, and hoping to save himself and his family, he defected and joined the Olympians. With Prometheus' help, Zeus and the Olympians defeated Cronos and the old gods and banished them to Tartarus, a gloomy abyss far deeper and darker than Hades.
Prometheus was a clever deity, a master craftsman and creator. He created man, and taught man the many crafts that were necessary for man's survival. But man lacked a crucial gift: fire, sacred to the gods, denied to man by Zeus's command. In the version of the story chosen by Aeschylus, Prometheus stole fire and gave it to man. As punishment, Zeus had Prometheus chained to the rocks of a desolate mountain wilderness.
The play begins here, as Might and Violence enter, restraining Prometheus. Prometheus remains silent as they hold him down, and Might heaps abuse on him. Reluctantly, Hephaestus, smith of the gods, chains Prometheus to the rocks. Hephaestus is a compassionate deity, and he shows that he has no love of his duty. Yet he must obey Zeus. The captors leave Prometheus alone, and the titan laments his fate. He knew his crime when he committed it, but the punishment is excessive and cruel. The daughters of Oceanus, who constitute the play's chorus, enter. They have come to comfort him, and to hear the story of why and how Prometheus has come to be chained. Oceanos enters later, announcing his intent to go plead on Prometheus' behalf to Zeus. But Prometheus warns him that the plan will only bring Zeus's wrath down on Oceanos, so the sea god does not go. He exits, but to return home rather than go to Olympus.
Io enters. She was once a consort of Zeus, and will be again, but in the meantime Hera's wrath has led to Io being transformed into a cow. She is pursued by a gadfly to the ends of the earth. She begs for Prometheus to tell her the future, and he warns her that her wanderings are only beginning. He does assure her, however, that one day she will find a home and be the mother of a great family; from this line, Prometheus' deliverer will come. Prometheus tells Io and the Chorus that he has knowledge crucial to Zeus's survival as ruler of the gods: one day, the king of the gods will make a marriage that brings about his downfall. Io leaves, to continue on her arduous journey.
Hermes arrives. Zeus has heard of Prometheus' secret knowledge, and Hermes has come, under Zeus's orders, to threaten Prometheus with torture. Prometheus refuses to tell what marriage will destroy Zeus. The play ends with Prometheus being tortured with fantastic and terrible pains: organ devouring beasts, lightning, pain that will not end because Prometheus is a titan and therefore cannot die.