Satan and Evil Angels

Evil spirits, in the beginning created sinless, were equal in nature, power, and glory with the holy beings that are now God's messengers. But fallen through sin, they are leagued together for the dishonor of God and the destruction of men. United with Satan in his rebellion, and with him cast out from heaven, they have, through all succeeding ages, cooperated with him in his warfare against the divine authority. We are told in Scripture of their confederacy and government, of their various orders, of their intelligence and subtlety, and of their malicious designs against the peace and happiness of men....TA 11.2

None are in greater danger from the influence of evil spirits than those who, notwithstanding the direct and ample testimony of the Scriptures, deny the existence and agency of the devil and his angels. So long as we are ignorant of their wiles, they have almost inconceivable advantage; many give heed to their suggestions while they suppose themselves to be following the dictates of their own wisdom. This is why, as we approach the close of time, when Satan is to work with greatest power to deceive and destroy, he spreads everywhere the belief that he does not exist. It is his policy to conceal himself and his manner of working....TA 12.1

It is because he has masked himself with consummate skill that the question is so widely asked: “Does such a being really exist?” It is an evidence of his success that theories giving the lie to the plainest testimony of the Scriptures are so generally received in the religious world. And it is because Satan can most readily control the minds of those who are unconscious of his influence, that the Word of God gives us so many examples of his malignant work, unveiling before us his secret forces, and thus placing us on our guard against his assaults.TA 12.2