I do not profess to know when Satan decided that he no longer wanted to serve God, but the Bible is clear that when he did, a third of the angels foolishly followed him (Ezekiel 28:12-20; Revelation 12:4). It appears that he went from being Lucifer, the anointed cherub and light bearer of God (Isaiah 14:12), to being the serpent, the tempter of man (Genesis 3:1-16). The Bible uses no less than eighteen names to describe the enemy of God and man. In Revelation 12:9 alone, he is called the great dragon, that old serpent, the Devil, and Satan. He is called "the prince of the power of the air, the spirit that now worketh in the children of disobedience" and he controls "principalities, powers, rulers of the darkness, and spiritual wickedness in high places" (Ephesians 2-2;6:12). He is called, "the accuser of the brethren" in Revelation12:10. Other ominous names for him are: the evil one, Abaddon, Apollyon, roaring lion, Beelzebub, Belial, God of this world, enemy, murderer, and liar.
In Hebrews 2:14, we are told that the devil has the power of death. In 1 Corinthians 5:5, he has the power to destroy physical life, and in 10:10, he is "credited" for destroying thousands of lives in the wilderness when the people murmured against God. In Job 2:6, Satan was permitted to kill his children and inflict pain on Job, but was forbidden to take his life. The fact that God told him not to kill Job, clearly shows that Satan could have, and certainly would have if God had not restricted him. We can get a glimpse of his thirst for the souls of men from the Parable of the Sower (Matthew 13:4 and 19); the effort of God to plant seeds of faith was immediately hindered by Satan removing them.
When I think of Satan, I picture him being like a large reservoir of water being held back by a huge dam. The dam is God, and He allows some of the power to be released to accomplish His purposes with man. Satan is allowed to tempt us, but he is limited, even in that (1 Corinthians 10:13). He is allowed to take lives, but only when it will ultimately work out for good for His children (Romans 8:28). He has the ability and the will to destroy everyone and everything, but not without God's permission. There is a key word in First Peter 5:8, which really sums it all up. "Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour." We all learned early in school that when wanting to do something, we were not to say, "Can I ..." but were to say, "May I ..." The use of the word may implies that the one asking is under the control of the one being asked. The action requires permission. Thank God that He loves us and limits such an evil entity! And thank God He does not give us what we deserve!