Ye are of your father the devil, and the lusts of your father ye will do. He was a murderer from the beginning, and abode not in the truth, because there is no truth in him. When he speaketh a lie, he speaketh of his own: for he is a liar, and the father of it (John 8:44).
The third verse of the Reformation hymn, A Mighty Fortress is Our God, focuses on the certain end of Satan. God has willed a mighty triumph through His truth.
And though this world, with devils filled, Should threaten to undo us, We will not fear, for God hath willed His truth to triumph through us: The Prince of Darkness grimWe tremble not for him; His rage we can endure, For lo, his doom is sure, One little word shall fell him.
When Satan was cast from heaven, fully a third of the angels fell with him (Revelation 12:4), such that a Legion of them could inhabit one individual (Mark 5:9). They are evidently everywhere, doing Satans bidding, giving him the power to accomplish his malevolent desires.
But God has other plans for His children. He desires to turn them from darkness to light, and from the power of Satan unto God, that they may receive forgiveness of sins (Acts 26:18). He desires us to resist the devil (James 4:7), and not give place to the devil (Ephesians 4:27).
He also has plans for Satan, including everlasting chains under darkness (Jude 6), and everlasting fire, prepared for the devil and his angels (Matthew 25:41). Just one little word, and Satan will be cast into the lake of fire and . . . tormented day and night for ever and ever (Revelation 20:10).
Jesus, anticipating His coming execution, spake of it in triumphant terms. This had been His Fathers will all along. Now, He said, shall the prince of this world be cast out. And I, if I be lifted up from the earth, will draw all men unto me (John 12:31,32) and now the battle is His. JDM