I will post the entire passage from the Bible down below. But I just want to summarize in my own words. First of all, there is a demon-possessed man from Gerasene.
Where is Gerasene?
I looked up the location of "Gerasene", i.e. where is someone from is they are a Gerasene. Wikipedia says the following:
[The] "country of the Gergesenes/Gadarenes/Gerasenes" in the New Testament Gospels refers to some location on the eastern shore of the Sea of Galilee. The name is derived from either a lakeside village, Gergesa, the next larger city, Gadara, or the best-known city in the region, Gerasa.
It shows the following picture. Of note, it is in the region of the Decapolis (a group of ten cities on the eastern frontier of the Roman Empire in the southeastern Levant in the first centuries BC and AD.)
Wait, what? He "lived among the tombs."? What does this even mean? He just lived in a graveyard among tombs. Such a strange way to live. Just imagine for a moment a man living in a graveyard all day long. Where does he get food? Where does he sleep? It's so mysterious. Why was he there? I feel he is there because the demons liked to be there around all the death.
Wow. "No one" could bind him? That's rather incredible. It seems they had put much effort into constraining this man. His demon-possession seems to have given him extra-human strength. It's another sign of possession. To have this kind of unhuman strength, to be able to break free of fetters and chains? Think about that, it would take physical power many times greater than even the strongest man possesses. Truly incredible strength. Again, this came from the demon possession, which goes to show the power of this type of Satanic interference. This was not mere mental illness. No mentally ill person just suddenly has the strength of 10 or 20 men. This definitely fits the criteria for possession. If you look into some indicators sought out by exorcists, one of them is super-human ability such as impossible strength or ability to know things that are essentially unknowable.
What does this name indicate? Fr. Hardon, a renowned Catholic scholar, wrote "Some of the possessed were controlled by several demons (Mark 12:43). In one case so many devils possessed a man that their name was Legion."
That was just a little side note there. But it shows the gravity of the situation. It's like saying he was possessed by 5,000 demons. But more important than showing the power of the demons, it shows the power of Christ to overcome evil. No amount is even a tiny blip to Christ. As some saint once put it, God's mercy is like a raging furnace into which a tiny drop of water is thrown. The tiny drop of water represents even the most serious sins.
Mark 5: 1-20
Jesus Heals the Gerasene Demoniac
5 They came to the other side of the sea, to the country of the Ger′asenes.[a] 2 And when he had come out of the boat, there met him out of the tombs a man with an unclean spirit, 3 who lived among the tombs; and no one could bind him any more, even with a chain; 4 for he had often been bound with fetters and chains, but the chains he wrenched apart, and the fetters he broke in pieces; and no one had the strength to subdue him. 5 Night and day among the tombs and on the mountains he was always crying out, and bruising himself with stones. 6 And when he saw Jesus from afar, he ran and worshiped him; 7 and crying out with a loud voice, he said, “What have you to do with me, Jesus, Son of the Most High God? I adjure you by God, do not torment me.” 8 For he had said to him, “Come out of the man, you unclean spirit!” 9 And Jesus[b] asked him, “What is your name?” He replied, “My name is Legion; for we are many.” 10 And he begged him eagerly not to send them out of the country. 11 Now a great herd of swine was feeding there on the hillside; 12 and they begged him, “Send us to the swine, let us enter them.” 13 So he gave them leave. And the unclean spirits came out, and entered the swine; and the herd, numbering about two thousand, rushed down the steep bank into the sea, and were drowned in the sea.
14 The herdsmen fled, and told it in the city and in the country. And people came to see what it was that had happened. 15 And they came to Jesus, and saw the demoniac sitting there, clothed and in his right mind, the man who had had the legion; and they were afraid. 16 And those who had seen it told what had happened to the demoniac and to the swine. 17 And they began to beg Jesus[c] to depart from their neighborhood. 18 And as he was getting into the boat, the man who had been possessed with demons begged him that he might be with him. 19 But he refused, and said to him, “Go home to your friends, and tell them how much the Lord has done for you, and how he has had mercy on you.” 20 And he went away and began to proclaim in the Decap′olis how much Jesus had done for him; and all men marveled.