There’s a book that was a best seller in Greece that I highly recommend, called “The Gurus, the Young Man, and the Elder Paisios” by Dionysios Farasiotis. The book is a memoir about a young man (the author) in Greece in the 1960’s-1980’s who always had an obsession with mysticism, the occult, and summoning “spirits” in order to achieve an enlightenment to be “greater than God.” He gives Christianity a chance, and then decides to go to India and give Hinduism and occult practices the same chance he gave Christianity. He sees how daemonic these things are, and ends up becoming a faithful Christian for the rest of his life.
In the book, he details some of the things he experienced, such as group meditations, in which he was able to summon a “golden face,” and everyone in the room felt the intimidating presence of this spirit in different parts of the room, how he dreamed that he was attacked by a horned monster and woke up with pains and bruises where he had been attacked (his friend told him she had the same dream about him), and how a friend of his, in an argument with another friend, wrote some demonic lettering on his friend’s window to “summon a demon to teach him a lesson.” There was loud banging on the window in the middle of the night and for the rest of the night, and they could not figure out what it was.
One of the most interesting parts of the book, which in my opinion proves the validity of demonic posession, is when the author travels through India to see a man worshipped as a God, named Babaji. He witnesses strange things from the man, and as a line of people (him included) walks one by one in front of Babaji to receive advice or a blessing, the author crosses himself, asks for Christ to help him, and upon standing in front of Babaji, Babaji’s face turns to horror and malice and he screams at the author to get out of his sight. He didn’t do that with any other people in the line, but only the one who crossed himself and asked for the intercession of Christ.
So in short, yes, demons can be summoned.