from a biblical perspective...
for one thing, it is never the "deviL" . like pick4 correctly said, he was/is a created being. he got his start (if you will) as the highest of all angels, but because of his pride and his beauty (he still is the most beautifully created being then and since), he sought to rebel against God and was thrown out of heaven along with his "symphathizers" (demons). so unlike God who is omnipresent (everywhere at one time), satan, the devil or marilyn manson (jk), cannot be everywhere at once and he certainly has bigger fish to fry than us. but...
there are demons whose job description is one thing and one thing only, that of steering away people from Christ. they are already judged and condemned and it is their push to try and take as many with them as possible. their sole job is to get a person to think that anything (you fill in the blanks) will be thier "salvation" ....anything except for Christ. and it doesn't matter if they can lure you into the occult, or they can lull you to sleep with apathy. it comes in many forms and where most people see the obvious (thru the occult and things deemed "satanic"), they do thier best work mission impossible style .....right in the church masquerading as God/Christ himself just like ohioplayer showed you. "IF" Christ really is the answer, then that would explain why they target him. and if you are honest no matter what your belief system might be, you will see that it is so. you can talk to anyone about any religion or religious figure, but talk about Christ and people freak out and can't explain why they do.
ask "seth". in the seth books he takes a mere 'swipe' at organized religion (and is right in doing so as they always pepper a little "truth" to get you to swallow the whole "pill"). in the seth books, he seeks to reduce Christ to something less than the savior of the world. why does he go to such great lengths? why does he take up so much time and space in his books about being anti-christ? why not other religious leaders who claim to be the way as there are thousands of them. because demons oppose Christ ....because he is the answer. how do i know? because i do my homework instead being afraid of it and running the other way. i cannot defend against something blindly, i have to know "why" it's not good and then defend against it if need be by offering informed alternative information.
i don't personally look for demons behind everything that is "bad", as that is foolish. alot of the stuff we do comes from ignorance or willfull stupidity (lol). but i do recognize when they are at work behind something, because this stuff requires more than just a "guess". the "devil" didn't make anyone do anything, they chose to. but one thing that they are all about, is that they are the aiders and abetters for all things evil in nature. more accessories to the crime then the crime themselves. they are more than happy to get you to disobey God by tricking you if they can. the trick is that we are not suppose to venture into areas that God has stated are off limits in the 1st place. if you dabble in that, you open yourself up to them and subsequent deception and you need to turn away from it. know what God allows and what he doesn't and "color" inside those lines only (if you are remotely interested in what he thinks). definitely demonically influences in this world. 911 was a "window" into that world ....BIG TIME.
and they are perfectly happy if they can get you to think that they don't exist. they do thier best work flying low under the radar. thier best work to date ...religions. especially the ones that include Christ, but exclude his finished work on the cross (that somehow we still have to "work" our way into a place where God will "accept us"). Christ finished that "job" as the biblical narrative goes. we don't have to...
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angels...
also created beings that still choose to serve God. their purpose here on earth is to assist in carrying out Gods will. in heaven, thier sole purpose is to worship him.
not sure to be honest if there are angels that are assigned to us specifically, i will have to study up on that one. i do know that they are used of God at times to assist or intervene in our lives only when it becomes necessary in order to carry out his will. but before you run with that one there must first come a warning that the bible does give specifically about "good" angels as well. and that it is strictly forbidden in scripture to worship or give any "props" to any created beings, including angels. they know this and refuse worship as per scripture references whenever it was recorded that men had encountered angels and they tried to bow down and worship them.
we cannot pray to them or ask for their help as "help" comes only from God via a personal relationship. you cannot hold them in any higher regard as even yourself. they are the same as you, in that they are created beings. you cannot seek them out for advice/help. they cannot answer you and won't and the reason that they won't is because they are forbidden to by God because he knows that we will wrongfully give them credit than what he rightfully deserves.
their job is to assist and stay out of the way so as to not allow any possibilities that you might assign what they did as coming from them, instead of God. there are merely a tool (no more different than when God chooses to use us), and they are not anything more than that. anything beyond that is idolotry and idolotry defined is giving credit that belongs to something else, when it belongs to God. they know thier place and will never do anything that will lead a person into thinking that they are "special".
most likely in your lifetime, you will never see - experience one. unlike demons, they will never "speak" to you. demons are there to deceive a person where as angels are there only enough to facillitate Gods plan in your life. so demons if given the chance will talk to you, where angels won't. most likely if you are aware of them around all the time, that would be a red-flag as God doesn't want us to get all jacked about them an end up wronfully assigning what he is doing thru them - to them.
scripture does say that demons masquerade as angels of "light". be very carefull in what you are assigning your "help" to, and who you are asking for help. you could be setting yourself up for deception.
be thankful that God provides angels to assist him in his will for us and leave it at that. they are only created beings and not God.
20/20 TOOBRAINDEADTOTHINKOFANYTHINGCLEVER