I've seen them before. My wife has seen them. I've been with other people that have seen them. It seems to be something that is attracted or is visible under certain circumstances. My wife and I do not do any drugs other than caffeine. She might drink alcohol a couple of times a year, but I don't even do that.
It is like a mind thing. If I think about specific spiritual things my mind feels different than when I think about scientific things, programming, etc. It feels like I am changing gears when I switch between these phases.
It is when people happen to be in that spiritual side long enough and active enough that I tend to hear stories of encounters with these things.
We can defeat them, but I've often wondered if when we are in whatever this phase is we might not be like a lone torch lit in an area of darkness that gives a nice beacon to attract such things.
I haven't encountered anything like that for decades and I have my own way to deal with them if it were an issue. I've written about these things in a couple of posts in the past. [1 , 2, 3]
RE: My battle with a shadow being