Final answer:
The oracle's prophecy that Oedipus would kill his father and marry his mother is the catalyst for the tragedy in Sophocles' 'Oedipus the King,' directly influencing the plot and Oedipus' downfall.
Step-by-step explanation:
The Oracle that Plagued Oedipus
In Sophocles' tragedy, 'Oedipus the King,' Oedipus, the king of Thebes, is determined to lift the plague decimating his city. He learns from the oracle of Delphi that to end the plague, the murderer of the former king, Laius, must face justice. As Oedipus delves deeper into the mystery, he discovers, through the prophecy of the blind prophet Tiresias and the statements of other characters, that he himself unwittingly fulfilled a dreadful oracle foretold to him long ago: he killed his own father and married his mother.
This revelation demonstrates the central role that the oracle plays in the tragic life of Oedipus. The oracle's pronouncement sets the story in motion and ultimately leads to the play's tragic conclusion, in which Oedipus blinds himself, and his wife/mother, Jocasta, takes her own life. The audience is left to experience catharsis, having witnessed the unfolding of the oracle's grim truth.