When you ask most people what Christ accomplished in his incarnation/life/death/resurrection, most people will talk about how Jesus has saved us from our sins: "Behold, the Lamb of God, who takes away the sin of the world!" (John 1:29 ESV). When pressed, many will talk about how Jesus acts as our 'substitute', both in the sense of taking our punishment and fulfilling our God-given vocation. Such satisfaction or penal substitution theories are widely-held understandings of atonement, but they are not the only models, nor have they always been the dominant understanding of the work God has accomplished in Christ.
For the first thousand years of church history, the most widely supported theory of atonement was Christus Victor. This view held that Jesus' death and resurrection represented a rescue/liberation of humanity from the bondage of sin, death, and the devil. There is good biblical support for this theory. The apostle Peter summaries Jesus' ministry for Cornelius' household saying: "He went about doing good and healing all who were oppressed by the devil, for God was with him." (Acts 10:38 ESV). According to the New Testament Jesus came to "destroy the works of the devil." (1 John 3:8 ESV).
We live in a world that focuses on the material: what we can see with the naked eye. But the biblical world, and much of the Two Thirds worlds acknowledge another dimension that is a crucial part of reality: that "we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places." (Ephesians 6:12 ESV). The Good News we heard in today's 'sermon' is that Jesus has ultimately defeated these forces, that we do not need to live in fear of sin, death, and the devil.
A story is told about Martin Luther, who that one night he heard noises in his room. He lit a candle and checked to see if the doors were locked. As he turned, he saw the devil himself seated in a chair with a wicked smile on his face... "Oh, it's only you," said Luther, who blew out the candle and returned to bed.
Understanding Christ's victory over the forces of darkness offers us confidence and security and hope.