Equally significant is the introduction in "Macbeth" of the supernatural element to this play which is pivotal to the tragic downfall of Macbeth who goes from being lauded as a brave and fearless warrior--"O valiant cousin! Worthy gentleman!" as King Duncan calls him--to a loathed murderer--"Thou bloodier villain" as Macduff addresses him.
The belief in the prophecies of the witches that Macbeth hears is what impels him to his ambitions of power. He considers that he may not have to do anything to become king:
If chance will have me King, why,chance may crown me/Without my stir (I,iii,44-45)
This interest in the supernatural world captivates not only Macbeth, but the Elizabethan audiences as well who revel in such lines as "nothing is /But what is not" (I,iii,142). Indeed, themes of evil spirits and witchcraft were very popular in these times. When Macbeth returns later in the play to speak with the three "weird sisters" he is so disturbed by their next prophesies that he initiates his murderous actions to prevent his own demise. Of course, tragically he has been entrapped by this preternatural world of the witches.
Act I, Scene iii is the first appearance of the “weird sisters,” called the Witches. Banquo and Macbeth encounter them in the woods. The Witches address Macbeth as “Thane of Cawdor” and “King,” confusing the two soldiers because those two nobles are still alive and holding their titles. Banquo asks if the sisters have a prophecy for him as well. They predict that he will be “lesser” than Macbeth and “greater,” and that his sons will be kings though he himself will not. After the Witches disappear, two more soldiers greet Banquo and Macbeth and inform them that the king has named Macbeth Thane of Cawdor.
This scene sets the stage for the rest of the plot, that Macbeth will launch a quest for power and stop at nothing short of murder to achieve his ambitions.