I forgot to reply ... Tonight I have more time.
We agree. If you take a look to the general opinion from exorcists, they all agree that the main cause of those events that can end in possesion is playing with the occult, especially ouija/spiritism. We do not only consider that those "games" are a sin (lol, yes we believe sin exists unlike that New Age) against the 1st. Commandament, but also a way of entering in the land of Satan, where he and the ones that did follow him, are the kings. There's no need to say that the great most of the people that practise that do not even know, and fall in the trap: they believe they are talking to dead people, or to extraterrestrial beings, or to spirits ... lol ... all lie, yes, the devil seems to have a great imagination, a good actor. Here I repeat the same I said in a past post, if the devil (or devils, in plural, if you prefer) reveals himself, no normal man would follow him, so he has to lie, to invent anything, because though he would belove having human beings worshipping him, he knows he can't, so at least he gets happy having people worshipping anything but God, through lie, and pulling them towards sin, to disobbey God that forbade the practise of the occult. Other way is if he cannot do men practise the occult, at least to worshipp themselves, like he did worship himself. "If you research inside you, you will descover a huge potential, a positive energy, you are God" (New Age) "I will even say to you how to do it, with a sorcerer manual". Very sadly many men fall in the trap of all these false promises, and end doing what Satan wants: the removal of moral. "There's no any sin","There's no any objetive reality", "There's nothing stable", Moral Relativism.
Other sophisticate knot is the sincretism: having men mixing all religions, having a dozen of incompatible philosophies dancing all together in their minds. (New Age). For example, having many christians also acepting incompatible and opposed ideas with christianity, like reencarnation or that Ying and Yang, that oriental absurd philosophy. (We have demonstrated logically that an anti-God cannot exist). And not only mixing, but also picking, like a restaurant menu, the things one like of any religion, removing of course moral: picking only the things one find convenient at any time. Or having many christians worshipping an "Architect of the Universe". We can expect anything.
His first lie against humankind was to promise men that "you would be like God if you disobbey Him" (as if sin was something God invented to keep men in ignorance and to not remove Him out of his chair, to not let them realise that they are gods), to pull men to execute the same sin he did, bringing the same results that brought to him: man fell.
Of course, we believe the main job the devil (the devils) does is temptation (then, more rarely they can also go beyond that: infection, obsession, possession, commonly as result of practising with the occult). In a first step we have no way to distingish the origin of the temptations men suffer, some come from the world, others from flesh and others from the devil/s. We only can have some suspices, never 100%, that those temptations come from the devil when they are very strong, almost constant, during a long time and about matters that come suddenly, not from the normal behaviour or ambient of a man. For example, today we know that Teresa of Calcuta suffered the temptation from the devil, when still girl, from the day after she became nun, she started to suffer very heavy temptations against the existence of God, and never abandoned her.
The devil can also attack saints, injecting a "false mysticism", he even dares to take a "corporal image" of Christ. And by the way, the mysticism of New Age has nothing to do with Christian mysticism, they use the same word, but are contrary. New Age says a man that he can get the "level of union" by himself, simply efforting or making some sorcerer job, or taking drugs that "open the mind, and let energy flow", really seriously damaging those men. Christian mysticism to the contrary ensures that a man can only get that level of prayer (union) if God wants, if God gives him, no matter what that man does, and of course, a man cannot force God to do anything. Very sadly many men also fall into this sophisticate trap.
And of course, the devil (now I want to let clear, that we, catholics, when say "devil" in singular also mean the plural) tempts to do those practises of the occult, to stablish a "contact with him" that naturally have a serious risk and many times if not stopped in time ends in a disaster for men. He can only bring to men pain (in different ways), that's the only he has to give.