"When he saw Jesus from a distance, he ran and fell on his knees in front of him. He shouted at the top of his voice, 'What do you want with me, Jesus, Son of the Most High God? Swear to God that you won't torture me!' For Jesus had said to him, 'Come out of this man, you evil spirit!'" NIV translation
This man ran to Jesus and worshiped as he fell to his knees and even tried to speak but the demon took over his voice. In this, we once again see Satan trying to imitate the things of God as, in this case, he is imitating the indwelling of the Holy Spirit.
"Then Jesus asked him, 'What is your name?' 'My name is Legion,' he replied, 'for we are many.' And he begged Jesus again and again not to send them out of the area. A large herd of pigs were feeding on the nearby hillside. The demons begged Jesus, 'Send us among the pigs; allow us to go into them.' He gave them permission, and the evil spirits came out and went into the pigs. The herd, about two thousand in number, rushed down the steep bank into the lake and were drowned." NIV translation
It seems kind of weird but Jesus has a conversation with the demons that were inside the man. Imagine what was going through the minds of the disciples as they stood there and listened. We notice that they had to ask for permission to do anything and it is a reminder of Jesus' authority over all the spiritual realms as well as nature.
"Those tending the pigs ran off and reported this in the town and countryside, and the people went out to see what had happened. When they came to Jesus, they saw the man who had been possessed by the legion of demons, sitting there, dressed and in his right mind; and they were afraid." NIV translation
Those that witnessed this ran to spread the news of what had happened and the people gathered to see if it was true.
"Those who had seen it told the people what had happened to the demon-possessed man - and told about the pigs as well. Then the people began to plead with Jesus to leave their region." NIV translation
Once again, we see that the people were looking for physical healing but wanted no part of the spiritual.