Yes, they exist. It's surprising where you can see them if you know what to look for. Their favourite place is inside a host - a person - but anywhere will do whilst they are waiting for the next host to come along.
They do not have to hide from daylight, do not have ultimate power, do not respond to religious chantings - until the name of Christ is uttered and even then you must believe to have any effect. They do not make themselves obvious by levitating their host or throwing things around, they are far too crafty for that.
Their purpose is to cause chaos, disruption, damage, fear and grief. All negativity is like nectar to them, so the more they create, the more well fed they are. They operate in the ether of the earth, they are attached to the earth and survive on man's fear. The earth is polluted with man's fear and thought forms making the astral plain a nightmare to navigate.
Demons look for the weak. Drugs, alcohol, sex, gambling, addictions, violence and fear are all signs of weakness. Not in the sense that you and I understand weakness but the weakness of the aura - the protective shield around each and every one of us. The aura is weakened by such activity and becomes holed, such holes are easy for the negativity or demonic entity to slip into. Once a demon is inside an aura they become attached to the host and the problems really start.
But, don't become scared to have a drink, smoke a cigarette, have sex. It doesn't work like that, it happens over time, the thoughts of the victim causing the damage more than the activity they partake in. Don't become fearful of the fear. Sounds easy doesn't it?
Having a normal social life and balancing it with good habits of cleanliness, exercise and healthy thoughts will keep the aura whole and repair it when it does wear thin. Laughing a lot and loving yourself and others is the best protection you can have.
If you know yourself well enough you can recognise when you have an attachment or an unwanted entity whispering in your ear and we have experienced it at some time or other in our lives. Your thoughts can take a downward turn, leading you to think more negatively. You become jealous of other's success, you find people more sexually attractive but you lust after them rather than want to get to know them. You may throw your money around more, drive too fast, swear too much, have sex too vigorously, drink too much, eat less, sleep less, try to manipulate others, steal, develop bad habits, nail biting, spitting etc., change your appearance, bitch more, try to belittle others, boast, want to be the centre of attention, be rude, be lewd, be afraid, turn up late for work, miss work, let people down, make sick jokes, be aggressive and lie.
All the above can happen at varying degrees from just having a couple of off days and shaking off the demon to being in full possession and acting drastically out of character.
Some of you will be able to see the demon. It's not as scary as it sounds. A possessed person will display behaviour that you will find unsettling as above and sometimes you may catch a look that crosses their face that you can't identify but which sets you on edge. I usually see black blobs, like ink, moving across and within the eyes, it's unmistakeable to me.
Above all use your instinct, out instincts are rarely wrong and serve as our protection, we should listen to it more than we do. Trust yourself.
If you think that you have a problem with an attachment, stop your vices for at least 3 weeks, live cleanly, be boring, that way the attachment has no hold over you and you are no fun for them. Say a prayer of protection, if you don't believe in the power of the Christ, ask whoever you do believe in to help you instead. See a healer if you want but only one that can deal in such infections because one that doesn't can cause deeper damage. Go to church and ask to be blessed. Finally demons are not all powerful - but you are - take control and tell it to go away.
Some people will never experience anything like the above symptoms and will say that demons and spirits do not exist - they are wrong. I have witnessed too much to think otherwise as have many exorcists, priests, mediums, therapists. In the past I conducted a workshop for a practising psychiatrist and a practising psychologist who both worked intensly with mentally ill and psychotic patients and prisoners. They had seen things that they could not understand nor reconcile with their medical knowledge. We had a meeting of minds and with my input of the spiritual realm managed to explain and solve many of their puzzling cases. Medicine is moving forward and becoming more open towards the mind/body link.