What literary device is used in the qoute "There might also be a dragon with five legs in my house, but no one has ever seen it."

The literary device used in the quote "There might also be
a dragon with five legs in my house, but no one has ever seen it" is verbal irony. More
specifically, the device is sarcasm.

Sarcasm is considered
verbal irony. Verbal irony is not only known as when a person says or writes one thing
and means another, but also (in regards to sarcasm) as an expression where sneering,
scorning, or jesting is done in order to show personal disapproval in the guise of
praise of a person, a situation or thing.

Therefore,
Proctor (in Act III) is being sarcastic through his use of verbal irony. Readers know
that there is no five legged dragon in his home. He is simply saying it to make a
point.