As far as I know “sa’ tan” or satan, means “no name” or “one who has no name”. In the book of Job the devil is given this name, to show his “no-thingness” before God.
So what can and can’t the devil do?
As I understand the devil(s) cannot create anything, all they CAN do is pervert whats already there, i.e. take good things and stop them from working properly.
Just as darkness is not an entity in itself, rather it is the absence of light; so too evil is not an entity in itself, rather it is an absence of love. The more absent light is the darker it gets, the more absent love is the more evil something becomes.
The devil(s) have, by their own choice, refused to love, and so seperated themselves from God’s love for all eternity, and are “Hell bent” on doing the same to us. (pun intended)
The only authority that the devils have, is that which is given to them. Usually by Man. God made us rulers over this world and has given us His authority, by giving us the ability to “Choose” **between **right from wrong( free will); but not to choose what **is **right and wrong, that is for God to decide, this is what caused “the Fall of Man”, when we decided that we could “be like God” and thought we could choose what was good and bad. The devils manipulate us, frail human beings, into giving them control of areas of our lives and in some cases our whole selves. God permits it because He respects His word, even if we do not. If we “will” that fallen angels take control, then God respects your free will, He will not make you choose to love Him. God warns us in scripture that if we do not turn from evil, He’ll take it that this is what we want, and so turn us over to the evil ones. He takes what we do seriously, even if we do not!
St Pio (Padre Pio) said " The devil is like a dog on a chain, he can only get you when you step outside the safe zone"
The only cases of possession I know of where the person hadn’t given themselves over to be a possession of a demon, was when those with rightful authority over them did so, i.e. Parents or rightful Guardians consecrating them to the dark side.
I believe the the devil can only do what WE allow him to, and with our frail fallen nature, we probably give him a lot more than we realise. But thank God we’ve got a Savio(u)r.