Elder Paisios the Athonite (+ 1994) was asked:
Geronda, why is it that people often resort to deceivers to solve their problems?
Because the devil has worthless gifts to offer and people can acquire them cheaply. What is asked of them doesn't carry a cost, and they can remain comfortable in their passions. Instead of repenting for the sins they commit as human beings, and instead of going to a Spiritual Father to confess, they find some deceived individuals - that is, the devil himself - and ask him to solve their problems. But when they suffer even more, they can't understand that the devil has control over them.
Geronda, how do people come to believe the deceived?
People are confused. So many people claim to be leading the people on the right path, while in fact they are carrying a big bag on their shoulders with the devil hidden inside! But the benevolent God does not allow him to be entirely hidden. Once in a while the devil sticks out a horn or his tail, the people see it and shout in fear, "What is this? A horn? A tail?" But the deceivers answer, "No, of course not! What are you saying? It's an aubergine!" And they say such things to fool the people and to present diabolical things as good and beneficial.
Geronda, how can a person be protected from such deceivers?
This can be done by remaining within the fold of our Church. Of course, if someone should out of ignorance follow some deceiver, God will not abandon him. God will help him recognize his mistake and return to the truth.
From Spiritual Counsels (vol. III): Spiritual Struggle, pp. 250-251.