26 Then they sailed to the country of the Gerasenes, which is opposite Galilee. 27 When Jesus had stepped out on land, there met him a man from the city who had demons. For a long time he had worn no clothes, and he had not lived in a house but among the tombs. 28 When he saw Jesus, he cried out and fell down before him and said with a loud voice, “What have you to do with me, Jesus, Son of the Most High God? I beg you, do not torment me.” 29 For he had commanded the unclean spirit to come out of the man. (For many a time it had seized him. He was kept under guard and bound with chains and shackles, but he would break the bonds and be driven by the demon into the desert.)30 Jesus then asked him, “What is your name?” And he said, “Legion,” for many demons had entered him. 31 And they begged him not to command them to depart into the abyss.32 Now a large herd of pigs was feeding there on the hillside, and they begged him to let them enter these. So he gave them permission. 33 Then the demons came out of the man and entered the pigs, and the herd rushed down the steep bank into the lake and drowned.
34 When the herdsmen saw what had happened, they fled and told it in the city and in the country. 35 Then people went out to see what had happened, and they came to Jesus and found the man from whom the demons had gone, sitting at the feet of Jesus, clothed and in his right mind, and they were afraid. 36 And those who had seen it told them how the demon-possessed man had been healed. 37 Then all the people of the surrounding country of the Gerasenes asked him to depart from them, for they were seized with great fear. So he got into the boat and returned. 38 The man from whom the demons had gone begged that he might be with him, but Jesus sent him away, saying, 39 “Return to your home, and declare how much God has done for you.” And he went away, proclaiming throughout the whole city how much Jesus had done for him.
Other accounts from the Gospels flesh out different emphasis from this story but what strikes me the most prominently in this account is the authority by which Jesus commands the demons to come out of the man. It's been said that the specific death of these pigs, which were intended for food, did more for the people in this area (and us, by way of the story) than if they were eaten. Why? It shows, as a declaration, that Jesus has authority over the forces of darkness. Jesus also said, "In the world you will have tribulation (troubles). But take heart; I have overcome the world." (John 16:33) He is able to free us from darkness because he has authority over it and has already overcome it.