If I understand correctly: When God created the "heavenly host", they too were given free will, and Lucifer was the most beautiful of Archangels (?), and somehow that went to his head, he became jealous of the Creation of Mankind, and he set our to destroy everything God had made. He was cast out of heaven and basically fired by his Employer, and is seeking his revenge by his limited power and influence. We, as Humans with free will, have the choice of whether or not to listen to his nonsense or to listen to the wisdom of God.