The Duke uses verbal irony when speaking to Angelo after he casts off his disguise and finally “returns” to Vienna:
O, your desert speaks loud, and I should wrong it
To lock it in the wards of covert bosom
When it deserves with characters of brass
A forted residence ’gainst the tooth of time
And razure of oblivion. Give me your hand
And let the subject see, to make them know
That outward courtesies would fain proclaim
Favors that keep within.
Here, the Duke is saying precisely the opposite of what he means, exemplifying verbal irony: though he outwardly compliments Angelo for his leadership of Vienna, he in fact intends to shame him for his hypocrisy and cruelty. Much of the language in his speech is deliberately ambiguous. He does not clarify, for example, why exactly Angelo’s actions deserve to be written in brass as a tale to be told in the future. Though the Duke apparently means that Angelo will be a legendary figure of good leadership, he in fact means that Angelo will be an infamous example of tyranny, like the many villains of history. The exaggerated nature of the Duke’s praise sharpens the sense of irony and sarcasm, as he is well aware of Angelo’s true nature.