Every great story that is in human literature or on the screen is written as a reflection of the Great Story that God has written in His Word.
Within every great story is a hero and a villain. Think of some of the great stories and movies of our time. The Hobbit and Lord of the Rings Trilogy were a fellowship of heroes band together on a quest to save what is good and noble all the while battling against evil. In Gladiator Maximus is the hero and battles Commodus the villain. In the movie Braveheart William Wallace is the hero and defies the villain Edward the 1st. Think of the most recent Marvel movies where the heroes battle the evil villains to save the earth.
Jesus is the Great Hero of our story that is continuing to unfold. There is also a villain in our story and that is satan and the demons he commands. We are in a battle of two kingdoms and Jesus our King has defeated the enemy through His death, resurrection and ascension. Satan and the demonic are defeated but are not yet destroyed and so they war against us because we are made in the image of God. This is the story we find ourselves in and we must train for it.