'Unclean Spirits' in the Bible

And they were all amazed, so that they questioned among themselves, saying, What thing is this? what new doctrine is this? for with authority he commands even the unclean spirits, and they do obey him.

And unclean spirits, when they saw him, fell down before him, and cried, saying, You are the Son of God.

And Jesus gave them leave. And the unclean spirits went out, and entered into the swine: and the herd ran violently down a steep place into the sea, (there were about two thousand;) and were drowned in the sea.

And he called unto him the twelve, and began to send them forth two by two; and gave them power over unclean spirits;