The Bible says that they were cast out of Heaven for their rebellion and they were cast down to Earth. They are here and have been since before Eden was a place where God created the first man. The Devil, Satan himself, tempted Jesus in the wilderness after His baptism. In the gospels, Jesus cast out many demons and spirits from people who were sick from their poisonous influence. The sicknesses took many different forms such as bleeding which couldn’t be treated by a regular doctor or diseases such as cancers or seizures. It is true that today we have “medical diagnosis” which places a cause for these in other means of infection.
But, how can even science be sure of those infections? Demons, spirits of disease, whatever name you give it, it is a way to turn a Christian away from God’s influence. These problems cause us to turn toward a doctor for relief, when Jesus can help in all ways far better than a doctor can.
In the books of Daniel and Isaiah, the fall of Satan is described and Jesus said that He saw Satan fall like lightning from Heaven to the Earth. Here are a few scriptures which detail this:
17 The seventy-two returned with joy and said, “Lord, even the demons submit to us in Your name.” 18 So He said to them, “I saw Satan fall like lightning from heaven. 19 See, I have given you authority to tread on snakes and scorpions, and over all the power of the enemy. Nothing will harm you.…
“How you have fallen from heaven, O star of the morning, son of the dawn! You have been cut down to the earth, You who have weakened the nations! Matthew 4:10
“Away from me, Satan!” Jesus declared. “For it is written: ‘Worship the Lord your God and serve Him only.'” Revelation 12:9
And the great dragon was hurled down–the ancient serpent called the devil and Satan, the deceiver of the whole world. He was hurled to the earth, and his angels with him.