We have seen many good things here on this earth , thus we have also experienced evil things too. In that manner we can say if God exists then we have to acknowledge the existence of evil spirits. These are the spiritual beings whom God kicked out from heaven. They are now ruling on this earth.
If we look at (Revelation 12:9)we can see that the large snake was thrown down into the earth. This is the Satan whom God removed from his glorious position. Satan is the one who leads the world away from the Lord. When Satan left heaven , he made a group and came down on the earth along with them.
Entrance and Power of Devils(Satan)
The Bible says that before creating this universe , the Lord created angels and they were created as spiritual beings. After the creation of angels , God created the world and on the seventh day man. God gave free will to both angels and man. But the Lord did not give them the choice of judgement. Adam and Eve were the first human beings whom the Lord created by his own image.
God wanted to make a fellowship with them . That is why they were sheltered in the garden of Eden where the Lord used to meet them. When Adam and Eve were in the garden , they had no work to do. When everything was fine , Satan came in the form of a serpent and tempted Eve to disobey the Lord.
Eve accepted the proposal of Satan and ate the fruit that the Lord told them not to eat. She also made Adam eat that fruit and finally both of them committed sin.
Among the angels there was Lucifer who was one of the most beautiful and powerful angels. Lucifer felt pride when he realized that he is powerful and beautiful. So, he wanted the position of the Lord as he was powerful. But he did not know that he is not powerful like God.
He wanted to take the position of the Lord and the honour from man. He wanted to rule the entire universe by his own will. When the Lord saw this, he removed Lucifer from his position (Isaiah 14:13-15). When Lucifer lost his position, he gathered one third of the angels from heaven and now they are altogether called Satan.
Works of Devils(Satan)
Satan or these fallen angels had done wrong against the Lord. The Bible says that Satan is a liar. By telling lies and tempting people , Satan is separating people from the Lord.
Satan is mighty but not like the Lord. Satan is walking around like a roaring lion to devour the children of God( 1Peter 5:8). The main job of Satan is to disturb the works of God and misguide the children of God. The Bible says that Satan is the ruler of this world( John 12:31). These fallen angels have the authority to enter into the human body and control them. Sometimes they also influence the people from outside. They also attack people with illnesses(Matthew 9:32-33), (Mark 5:1-20).
Apart from that these evil spirits make many troubles in human beings. Sometimes they cause physical weaknesses, mental depression, emotional problems etc.
Satan also attacks the children of God spiritually. When Satan works for someone, he cannot forgive others(2 Corinthians 2:10-11). He will always try to take revenge. The person will act inhumanly. Satan also controls the man of God to lie by taking the name of Jesus (1John4:3). Jesus told us not to take the name of the Lord. Because he is in heaven and we are on the earth.
Satan also works some miracles to get the attention from the people. He also performs some miracles to win the hearts of the people. Many people run after them by seeing those superhuman acts.
The Punishment of devils(Satan)
God gave authority and power to Satan for just a limited time. God knows their future and allows them to rule the world. Satan also knows that he will be put to an end at the right time.
When Jesus was on the earth ,he casted out demons from many people and one day those evil spirits asked Jesus , did you come to destroy us before the time( Matthew 8:29, Luke 4:34).
They know very well that they will have to stand in the judgement for their disobedience. The Bible says that the hell was created for the fallen angels and the people who will follow them will be thrown into the lake of fire( 2 Peter 2:4, Revelation 20:10).
The Bible warns us not to fall in the traps of those fallen angels. The word of God told us not to believe every spirit. We need to verify every spirit whether it comes from the Lord or not.