In the story "The Pardoner's Tale", Chaucer, who is the Author, uses a great deal of irony. Chaucer is a master of both Verbal and Situational Irony. What is the difference you say? The difference is quite simple. Verbal irony comes from the mouth. It is when you say one thing and mean another. Situational Irony is when what actually happens is different from what you expect. Summarily, Irony is a discrepancy between expectations and reality.
"But let me briefly make my purpose plain; I preach for nothing but for greed of gain and use the same old text, as bold as brass, Radix malorum est cupiditas. Radix malorum est cupiditas, meaning literally, "the root of evil is desire". Those very first words mark the beginning of the Tale's prologue. It helps with understanding the characteristics of the pardoner. The pardoner sells relics to those who are in need of a relieved heart, but only to those who can afford one. When I say "relieved heart", I mean those who have sinned. Inversely, he is committing the sin of avarice by being a greedy man. He pardons honest people who are genuinely forgiving themselves, all while in the process of committing sin himself. You see, this is an instance of situational irony. "To have my absolution for a shilling""come forward, Host, you shall be the first to pay, and kill my holy relics right away." You have to pay for the thoughts of forgiveness to a man who cares for nothing but pecuniary. This instance of Irony is quite overt. .
Now let me put forth an instance of verbal irony which you already know comes verbally. "Sell me some poison if you will, I have a lot of rats I want to kill and there's a polecat too about my yard that takes my chickens and it hits me hard, but I'll get even, as is only right, with vermin that destroys a man by night." The young man, who said this, was the man who was sent to fetch bread and wine. The "rats" in this case were the two men he was fetching for.