Through the witches only appear briefly in Macbeth, the witches have an impoartant function in Macbeth. The play opens with their grim and stormy meeting, and this contributes to its pervasive tone of mysterious evil. [ Macbeth is a play filled with evil. It lurks around in every scene. Some aspect of it is shown here and there which is why the tone of evil is pervasive.] The witches also serve as an enactment of the irrational. The supernatural world is terrifyin