Okay, this is probably a difficult matter for me to tackle, but I want to try it, if only to see how progressive christians respond to it.
The issue is this, I am diagnosed with schizophrenia for about 14 years now. And for quite a length of time in it I was told by conservative christians that my medical problem has to do with demons. I cannot remember to ever have had to do with the occult, beyond listening to some gothic music when I was young, and having had some juvenile, short and, for me, rather meaningless engagement with satan when I was a youth.
If I would describe it, then I have to say it's like this, sometimes in my mind I hear voices. They tell something about this or that, but usually they seem to try to change my thoughts, or maybe I can say they are like second thoughts that involuntarily contradict my own thoughts. For example, if I wanted to think, God is good, I might hear a thought in my head that says, God is shitty, or something like that. When this occurred for the first time, while i was trying to become a christian, in a conservative christian setting, I was immediately very terrified that I might become damned for such thoughts because they would constitute blasphemy of the Holy Spirit. I was very unsure about what to do with this, and the following years were very hard. I had a very troubled mind, experienced hallucinations of people coming into my room and playing Jesus and chiding me. When I read the bible I heard the words repeated in an angry and raging tone which only ended when I began reading different translations like the one from german chassidic jew Martin Buber.
Nowadays I have more mental sanity after a new bottom-up medicine change that my new doctor searched out for me. I am only taking as minimal dosage of neuroleptics and ironically this works much better than my previous heavy medication under which I had lot's of hallucinations and was very delusional about people frequently.
But while I am emotionally better off now without the old feelings of fear, I am now anxious not to fall into the strange old conservative traps again, and following the bottom-up change of medicines I also want to renovate my beliefs from bottom-up. For example, I don't quite believe anymore that I ever had demons or that such beings actually exist, I think it is more sensible to assume that I was simply sick. Also, there are many many people on this world, the majority of us in fact, who never have issues with demons or devils while conservative christians insist that the devil is a persistent and world-encompassing problem. One solution that I found was that the devil, in a reading of the bible, is just a synonym for true evil in general. He doesn't really exist, much like evil and sin don't have a genuine existence like matter and life. But in other ways, evil does exist, and very much so, because many people suffer from evil things in the world.
But, and this is another explanation that I found, much of the problem of good and evil has to do with our skewed perception about these things. Remember the story of paradise and the tree? We were allowed to eat from every tree, the tree of beauty, of humour, of wisdom, of fun, of love, of longing, of art, of science, of stories, of politics, of war even, they were all okay for us. But we were not supposed to "base our knowledge" on the good and evil dualism. Because, whenever we find something good, our minds are now bent to fear an evil that might destroy the good, or whenever we find something evil, our minds are bent to seek to destroy it or fear its destructive powers. The knowledge of good and evil does not lead us to fight the evil with the good, it leads us to be perceptively caught up in morality systems instead of being safe and sound in ethical and philosophical systems. For example, I think it is wiser to combat what we call evil by using the powers of truth and wisdom and love, instead of simply sacrificing another good thing to it. A good iteration of this is how Jesus saw love of the enemy. Normally the enemy is the evil person for us, and it is good to fight him with all your power until you have won out over him. But the wise person turns the enemy into a friend so that there would not be a lifelong struggle with all the hate, envy and revenge such struggles have inherent to them.
This is the kind of thing I'm thinking of now. Demons and devils really have no place in them, except in an explanation of how we can be misled much by living in a fantasy world of good and evil where there also agents of the devil. In fact, living in a struggle of good against evil under religious terms actually invites images of demons and devils for the mentally sensitive and fragile.