Earth that they were cast down. You and me (ie mankind) has a three fold nature: spirit, soul and body. The spirit is the real you andis the part where God can inhabit by His Holy Spirit. The soul is the mind, will and emotions and don't forget that animals who have no spirit do have a soul. Finally there is the body, the bit we can see and the place where the 5 senses reign.
Jesus arrived one day at a place on the shores of the sea of Gallilee and met a naked mad man. It transpired that this man was possessed, not in his spirit but in his soul, by many demons. The demons themselves begged to stay on earth longer and so Jesus cast them into the nearby herd of pigs (the pig's souls that is). The swine then promptly committed suicide by jumping off the cliff. The man was instantly and completely set free and "in his right mind". Great story...and it's true.
We have all heard that Jesus came to save the lost (includes us all..and His mother!) but few know that the word used in the original greek text is "Sozo" which means to "save, heal and deliver". This is exciting. The work of Calvery was to save our spirits, heal our bodies and deliver our souls from demonic activity, put a different way: it was a complete work! Remember that He publicly displayed every demonic power as defeated after His death (see Ephesisans Chapter 4). Now that's how we can truly see an end to destructive behaviour. Good News!