Except for Teiresias, all the characters in the play such as Oedipus, Iokastȇ, Creon, the messenger and the chorus know nothing about the proceedings of the story, so their speeches contain dramatic irony. Most dramatic ironies are found in the speeches of Oedipus. Almost every word uttered by Oedipus from the exposition of the play to the discovery is attributed with dramatic irony.
The play begins with the gathering of a group of suppliants before the palace of Thebes, who plead to Oedipus to save them from the dreadful pestilence, as he once did before. The dramatic irony begins with Oedipus’s first appearance. Every word is charged with dramatic irony, as well as the very situation. The pitiful townspeople have appealed for aid to the one who, in reality, is the cause of their woe, but both the people and Oedipus fail to understand it.
Dramatic irony is also found in Oedipus’ proclamation for finding out the killer of Laïos, when Kreon brings the news from Delphi that the city's peril is due to the shedding of blood of the last king, and the pitiful condition requires the banishment of the killer or the payment of blood for blood. Oedipus, at once, takes steps to find the killer and announces that if he makes confession of his guilt he will earn only banishment instead of death. The dramatic irony lies in the fact that the killer is unknowingly searching for himself. Thus the announcement greatly heightens the tragic effect of the discovery which comes towards the end of the play.
Another pitiable example of dramatic irony is found in the quarrel scene between Oedipus and Teiresias. Teiresias, knowing the truth, tells Oedipus that he himself is the killer of his father, husband to his mother, and father of his siblings. But Oedipus is quite ignorant about the true facts and mocks Teiresias cruelly. The dramatic irony lies here in our knowledge that though Teiresias is physically a blind man, he knows the truth and Oedipus, in spite of having eyes, is sightless. But the most suspenseful and tragic dramatic irony occurs in the scene between Oedipus and Iokastȇ and the Messenger. Each time Oedipus addresses Iokastȇ as ‘O wife’ or ‘My wife’, we shudder at the thought of the consequences that are to follow and feel great pity for Oedipus. Iokastȇ's words as she tries to disprove the oracles are also full of dramatic irony.
When the messenger arrives to inform Oedipus about the death of Polybos, Iokastȇ is overjoyed and cries triumphantly,
“O riddlers of God’s will, where are you now!
This was the man whom Oedipus, long ago,
Feared so, fled so, in dread of destroying him—
But it was another fate by which he died. (1.3.901-4)”
There is a palpable dramatic irony in Iokastȇ’s unbelief in oracles and she provokes the prognostications of the oracles. All remarks made by the Corinthian messenger are also full of dramatic ironies. The messenger tells Oedipus that he has brought the news that can please and may make grievous also. It is upsetting because Oedipus has lost his father and it is pleasant because Oedipus is going to be crowned soon. But dramatic irony lies in the messenger's ignorance that by bringing the news he only complicates the situation further. His news brings a reversal to the whole situation and after that there is no dramatic irony, as the truth is gradually revealed to each of the characters.
In the end, the truth is revealed to all the characters resulting in Iokastȇ’s suicide and Oedipus’s attack on himself ultimately taking his vision. Throughout the play the audience is well aware of Oedipus’s crime taking away any suspense for the ending though the characters themselves are shocked. The tool of dramatic irony has a great deal of power in a play setting. For Oedipus Rex, it is the difference between the audience waiting for another hint they know, or are tuning out. Sophocles was a true master of literature and effectively crafted Oedipus Rex into an engaging play whose characters and plot haunt continue its audience.