As I understand it, Satan was an angel who was cast out of heaven into the depths of hell. Did God create hell? Does Satan rule hell? Is hell a place? Is Satan just one person, or being, or are there many who help him? If Satan was cast out of heaven, how come he has so much “power”? Was Satan a living person millions of years ago, who died and went to heaven?
Let me direct you to a prior article "What is Hell Like?" to answer your questions about the existence and nature of hell. The lessons "Who is Satan?" should answer most of your questions about Satan. Finally, read through the article "Why Does God Allow Evil to Exist?" If you have further questions, please write.