What literary devices are used in Macbeth Act V, Scene 7?

As the opposing armies make their way toward his stronghold, Macbeth uses a metaphor to describe his situation. He says that his enemies have tied him "to a stake...bear-like." This is a reference to bear baiting, a blood sport popular in Shakespeare's day, in which bears would be tied to stakes and forced to fight off dogs until they finally succumbed. After setting the tone with this gruesome literary device, which reveals Macbeth's state of mind as the battle approaches, Shakespeare uses irony in two places in the scene. First, when Macbeth points out that young Siward, whom he has just killed, was "born of woman," and exits, only to be followed by Macduff, who, we find out, was not born of woman, having been delivered by Caesarian section. Then there is an example of classic dramatic irony. Siward describes the battle in terms that suggest that Macbeth's castle was taken with relatively little loss. "The castle," he says, "is gently surrounded...little is to do." He does not know that his son was among the dead before the castle walls, killed earlier in the scene by Macbeth. These are the main literary devices in this relatively short, but important scene.