The witches always signal doom and gloom in this play. The chanting and mixing animal parts in the cauldron creates the atmosphere of impending doom. Their very presence denotes elements of foreboding and the supernatural. Throughout the play, the supernatural is associated with evil and unnatural transformations. Macbeth and Lady Macbeth become unnatural (contrary to their nature) in order to kill. She asks to be “unsex’d” and he changes psychologically. By the end of the play, both characters are close to madness because of their fear and guilt.
The line that most obviously announces impending doom is when the Second Witch says “Something wicked this way comes.” Macbeth enters right after this. He has become wicked. Act IV, Scene 1 is also when the witches summon ghosts to show Macbeth visions of the future. At the end of this scene, Macbeth announces his plan to kill Macduff’s family.