I am not trying to convince anyone of my beliefs... I would not even call my warning a belief, but rather a friendly piece of advice from my very extensive experiences on this subject.
A lot of people who tell you that entities can not harm you and that there is no such thing as malevolent discorporate forces... do not even believe in discorporate entities at all. I won't point out names, but a few of the nay sayers here have said on other threads that they have not even ever encountered entities. Naturally, if you believe that the entities you encounter are all products of your overheated imagination, you will be quicker to dismiss the threats that they may or may not pose to you. To say nothing of those who have never even met any.
Schizophrenics and psychotics constantly rave about voices in their heads and evil spirits forcing them to do things they don't want to do. Even if such things are all in our heads, that doesn't mean that you can not be hurt.
I would say, instead of trusting your mental, spiritual, and physical health to people who have little or no experience with the subject... how about looking at the wealth of human writings on the subject?
Far from being a purely Catholic thing, nearly every spiritual tradition on the planet describes these beings and their negative, parasitic, and malevolent actions upon unwitting humans. The annals of shamanism alone are overflowing with examples. Every single African tribe I have ever heard of has beliefs and practices relating to spirit possession. All of them. From different language groups spanning 5000 miles and with no contact with each other. Nearly every Native American tribe has such beliefs as well. Brujos, curanderos, ayahuasceros, mescaleros... you would be hard pressed to find more than one native entheogen shaman who doesn't believe that these spirits are both real and dangerous.
The fact that these people who gave us basically all of the entheogens we have at our disposal (ayahuasca, peyote, mushrooms, salvia, yopo, virola, san pedro, ololhuiqui, iboga, voacanga etc. etc.) universally believe something... is probably enough reason to at least not dismiss the idea out of hand. It is the height of arrogance for people to take the plants and use them while simultaneously looking down at, and feeling superior to, the people who gifted them to you. Not unlike the Puritans at Thanksgiving taking the knowledge of pumpkin, squash, potato, corn and the rest and turning around and genociding the "savages" who gave them in goodwill.
Furthermore, it is not just the so-called primitive people who know about the dark entities. It litters the pages of Egyptian, Babylonian, Sumerian, Zoroastrian, Islamic, Hebrew, Vedic, Tibetan, Taoist, Shinto, Sikh, Jain, and Druz teachings. (The list is endless) From the Siberian Shamans to the Toltecs, The Tihuanacu to the Polynesians, from Indonesia to Norway, Zulu, Maya, Hopi, Mohawk... and Christian.
No religion save science doesn't accept these things AFAIK. The Bible teems with stories of demon possession. Fully half of JC and the Apostle's miracles involved the casting out of demons.
Believe what you want people. I am not here to proselytize.
But I can only say that I have personally seen people possessed by dark entities... and you do not want to be one. Eyes rolling in the back of the head, self-mutilation, committing of heinous acts, speaking in alien voices... even suicide. I know people currently locked in mental asylums that came back from journeys followed by malevolent conscious beings. This is not something to laugh at.
At least 3 people I know who had such experiences did not believe that they were even possible beforehand... they were clinical technicians and software engineers. Your disbelief won't save you. All three are currently locked in neuro-psychiatric institutes and force injected Haldol, Thorazine or even worse anti-psychotics.
If you alienate your protectors, and guardian angels... if you choose to abandon the light and think you can play willy nilly with powerful dark force... beware. Seriously... pride cometh before the fall.
Even those of us with decades of experience and training in the ways of knowledge, power, and warriorship would not be foolish enough to tempt fate by strolling into the darkest realms... and we know how to defend ourselves. Be wise, and listen to the angelic light beings. It is hard enough to keep your space clean and walk the light path free of ego and negative emotions... even with the help of powerful allies. Purposefully inviting dark entities into your space is just foolhardy.
I say all this with nothing but love and profound respect for fools and foolishness.
I do not say this to scare anyone or insinuate fear. Stick to the light and you will have nothing to fear most of the time.
My experiences on 5 continents show me that you need to be careful and not invite catastrophe upon yourself. These modern memes of embracing evil, attraction to darkness and other unwise stylistic affectations that are prevalent among the young westerners (goths, twilight lovers, death metal, satanism etc.) are an expression of the fact that such teens and young adults have no idea what they are messing with. They are like suburban rich kids who dress ghetto and then think they can stroll casually into Watts or Bed-Stye without getting robbed.
Just because some sad sack band tells you it is cool to explore the darkness... don't buy into their pathetic theater. Most of those eyeliner wearing dudes would vacate their bowels on a single 25mg toke of spice.