From an LDS perspective, what is an unclean spirit? What is its history? Where did it come from?
From the scriptures, I gather that unclean spirits want to inhabit mortal bodies. My guess is that unclean spirits once lived on earth in a mortal body.
EDIT: Some might say an unclean spirit is the same as an evil spirit and is the same as the third part of the host of heaven which fell in the pre-mortal existence. I would be happy to know if this is correct or if an unclean spirit is different than the other two.