The visions you’re referring to are those that are given to Macbeth by the three witches in Act IV. Following the prophecy the witches gave him at the beginning of the play, Macbeth is anxious to know what the conclusion will be, given that his wife has been having second thoughts. He seeks them out to “answer me / To what I ask you.” They respond by providing three speakers from their cauldron, and Macbeth sees their messages as a boon to his cause. He is told to beware the Thane of Fife (Macduff), that none of woman born shall harm him, and that he will not be defeated until Birnam Wood marches to high Dusninane Hill.
