Act III, Scene III is very short, as the murderers lie in wait for Banquo. Macbeth has enlisted them to kill Banquo and his Fleance, and thereby render impossible the witches’ prophecy that one of Banquo’s line would someday have the throne that Macbeth now possesses.
There isn’t a lot in terms of literary device in this scene, other than the usual dialogue that one expects in a play. There is, however, a nice piece of imagery early in the scene, when the First Murderer says:
The west yet glimmers with some streaks of day:
Shakespeare could have just had the First Murderer say, “It’s getting late in the day.” But that would certainly not be his style. By describing the appearance of the sky, Shakespeare puts a visual image in our mind. This was particularly important in his day, when the stage productions offered little in the way of scenery or special effects.
In Act III, Scene 3 of Macbeth, the three murderers enter to kill Banquo and his son. This third murderer has joined the other two from another direction; together, they wait to ambush the nobleman and son. As he and his son are attacked, Banquo cries out,
O, treachery! Fly, good Fleance, fly, fly, fly!
Thou mayst revenge. O slave! (3.3.25-26)
In these lines, the ambushed Banquo cries out to his son to flee as he realizes the treachery of Macbeth. His address to "treachery" is a literary device called apostrophe. Apostrophe is a figure of speech in which a nonhuman quality or thing is addressed as though it were present and able to reply like a person.