Marcus's Role
One example of situational irony in the play is the fact that Marcus is eventually excluded from Titus's plans and schemes. As a representative of rationality, sanity, and moral judgment, Marcus becomes a threat to the pursuit of Titus's vengeance, and Titus therefore keeps his plans a secret from his brother for most of the play. The irony, of course, is that Marcus's involvement could have spared Titus and other characters who end up dead at the end of the play.
The Metamorphoses
After Lavinia is raped and mutilated by Chiron and Demetrius, she is no longer able to communicate and therefore cannot name her attackers to her father. She starts reading the story of Philomena – a woman raped by Tereus – in Ovid's Metamorphoses. It is this story that inspires Lavinia to reveal her attackers by placing a staff in her mouth and carving their names into the sand. Thus, it is through another narrative of sexual violence that Lavinia ultimately invites Titus's revenge on Tamora's sons.
Revenge
When Tamora disguises herself as Revenge and reveals herself to Titus, there are multiple layers of dramatic irony at work. First, Titus is aware that the figure is actually Tamora, and therefore plays along with the charade. Tamora, of course, thinks she is fooling Titus, and this moment represents one in which the fortunes of the play start to shift (relatively speaking) in Titus's favor. The audience discovers that Titus has merely been pretending to be mad in order to pursue his revenge against Tamora, who, in this moment, is confident she has bested Titus for good.
The Pie
Of course, the most memorable example of dramatic irony in the play is when Tamora unknowingly consumes the remains of her two sons after Titus bakes them into a pie. It is a disturbing and grotesque moment in an already gruesome play, and one that ultimately catalyzes the demise of the majority of characters left on stage.
