The three Weird Sisters, of course, are the best examples of supernatural effects in Macbeth. They appear several times throughout the play. The most spectular occurrence comes in Act 4, Scene 1, when they offer to show Macbeth their "masters." Here Shakespeare shows a succession of "apparitions," the first being "an armed Head." The second apparition is "a bloody Child." The third is "a Child Crowned, with a tree in his hand." The fourth is "A show of eight kings, and Banquo last," intended to indicate that Banquo will have eight successors who will be kings of Scotland.
Another supernatural effect occurs in Act 2, Scene 1, where Macbeth sees a dagger suspended in the air in front of him and eventually follows it into Duncan's chamber to commit murder.
Another supernatural effect is described by Macbeth after he commits the murder. In Act 2, Scene 2, he tells his wife:
Methought I heard a voice cry "Sleep no more!
Macbeth does murder sleep"--the innocent sleep,
Sleep that knits up the raveled sleave of care,
The death of each day's life, sore labor's bath,
Balm of hurt minds, great nature's second course,
Chief nourisher in life's feast.