Legion

Legion is a demon mentioned in the Bible in the books of Mark and Luke. Legion, also called the Gadarene Demon, is a group of multiple demons with the habit of possessing the same individual. Jesus Christ is said to have met a man possessed by Legion on his travels through a region known as the Gadarenes, though other names are given in other places. When Christ met the man, they conversed. The most common version of the story is below:

And he asked him, What is thy name? And he answered, saying, My name is Legion: for we are many. - Mark 5:9

Being aware of the powers Jesus had, the demon begged for mercy, as none of them wished to be sent back to Hell. Jesus granted their wish and cast them out of the man then allowed them to reside in a herd of pigs. The pigs then turned and wandered into the Sea of Galilee, where they all drowned.

Sources:
Holy Bible; King James Version