Hello. You did not inform the play to which this question refers, which makes it impossible to formulate an exact answer. However, I will try to help you in the best possible way.
A monologue is a character's speech. This speech the character makes alone because he is expressing his deepest feelings and thoughts. This promotes a broad understanding of the audience with the character's actions, because the character is showing the most intimate of his being. Usually these speeches are emotional and have a strong appeal to the feelings of the audience, the actor and the character.
Initially Duncan is the king in Macbeth, however Macbeth later kills him and becomes king himself.
I am absolutely venerated to be here presenting this speech in front of you all, it is quite humbling.
Answer is foundation in historical facts or legends, and <span>dead/absent parent
supernatural creatures
universal themes</span>
