Here is a brilliant sample from Francis Frangipane's classic “The Three Battlegrounds.” I just read it and thought you would find it timely.
Satan's Domain: The Realm of Darkness
Many Christians debate whether the devil is on the earth or in hell; can he dwell in Christians or only in the world? The fact is, the devil is in darkness. Wherever there is spiritual darkness, there the devil will be.
Preparing for Spiritual Warfare
For most, the term spiritual warfare introduces a new but not necessarily welcomed dimension in their Christian experience. The thought of facing evil spirits in battle is an unsettling concept, especially since we came to Jesus as lost sheep, not warriors. Ultimately, some of us may never actually initiate spiritual warfare, but all of us must face the fact that the devil has initiated warfare against us. Therefore, it is essential to our basic well-being that we discern the areas of our nature that are unguarded and open to satanic assault.
Jude tells us, “And angels who did not keep their own domain, but abandoned their proper abode, He has kept in eternal bonds under darkness for the judgment of the great day” (Jude 1:6).
When Satan rebelled against God, he was placed under eternal judgment in what the Bible calls “pits” (2 Pet. 2:4) or “bonds” of darkness. The devil and the fallen angels with him have been relegated to live in darkness. This darkness does not simply refer to areas void of visible light. The eternal darkness to which this Scripture refers is essentially a moral darkness, which ultimately degrades into literal darkness. However, its cause is not simply the absence of light; it is the absence of God, who is light.
It is vital to recognize that this darkness to which Satan has been banished is not limited to areas outside of humanity. Unlike those who do not know Jesus, however, we have been delivered out of the domain or “authority” of darkness (Col.1:13). We are not trapped in darkness if we have been born of light. But if we tolerate darkness through tolerance of sin, we leave ourselves vulnerable to satanic assault. For wherever there is willful disobedience to the Word of God, there is spiritual darkness and the potential for demonic activity.
Thus Jesus warned, “Take heed therefore that the light which is in thee be not darkness” (Luke 11:35 KJV). There is a light in you. “The spirit of man is the lamp of the Lord” (Prov. 20:27). Your spirit, illuminated by the Spirit of Christ, becomes the “lamp of the Lord” through which He searches your heart. There is indeed a holy radiance surrounding a true, Spirit-filled Christian. But when you harbor sin, the “light which is in thee” is “darkness.” Satan has legal access, given to him by God, to dwell in the domain of darkness. Thus, we must grasp this point: the devil can traffic in any area of darkness, even the darkness that still exists in a Christian's heart.