Dramatic irony is a form of literary device that writers and authors use in their works that shows a contrast in the expected outcome. The readers or viewers know what is happening in the story but the characters in the story have no idea about it.
Ironies are a part of literary writings where the writers use literary devices to express or show things in one way but seems to be just the opposite of what is intended. And most importantly, it happens in a more sarcastic way, humorous manner. Dramatic irony is more concerned about the characterization in the story. The audience or readers know what a character says and meant but the characters in the story don't understand it.
In the Arthurian legends, we the readers know that Perceval is the knight King Arthur seeks. But the irony is that the characters in the story, each of them, have no idea about that. This is an example of dramatic irony.
