Verbal Irony: Gaveston's Death
Gaveston knows that he has run out of options, and that Edward cannot save him anymore. He says in response to the nobles telling him how he will die, "I thank you all, my lords. Then I perceive / That heading is one, and hanging is the other, / And death is all" (II.5.129-131). In his wry tone and ironic words, he conveys that all that is left to him is the ability to be a little sarcastic; other than that, his power has evaporated.
Verbal Irony: Warwick to Gaveston
Gaveston had hoped to see Edward one more time before he was put to death, and was even told this would be the case. However, he learns it is not to be so, and asks Warwick, "Treacherous earl, shall I not see the king?" Warwick replies with dripping and amused irony, "the king of heaven perhaps, no other king" (III.1.15-16). His evident delight in stymieing Edward and Gaveston's goodbye indicates just how far gone was Edward and his nobles' relationship is.
Dramatic Irony: Saint George
As the major battle is about to commence, the audience hears the nobles proclaim, "Saint George for England and the barons' right!" and then Edward proclaim, "Saint George for England and King Edward's right!" (III.3. 35-36). It is a bitter irony of history that each side thinks they have God, or, in this case, St. George, the patron saint of England, on their side. And as it turns out, neither side really triumphs, for loss of life and frustration of plans are rampant on both sides, and Saint George does not seem to favor either one.
Dramatic Irony: Lightborn
The sadistic Lightborn says to Edward, "These hands were never stained with innocent blood, / Nor shall they now be tainted with a king's" (V.5.81-82). The dramatic irony is that we know he has killed many people but not with his hands—he devises ingenuous ways to kill them that do not show how they died, and that is what he plans for Edward. He will use a red-hot spit and insert it inside Edward's anus, which does not stain or taint his hands. Of course, Edward knows none of this, owing to the sad irony of the scene.
