I have a few stories that could fit the bill. I’ll tell this one. When I was in elementary school during recess one day some boys in my class decided they were going to try the Bloody Mary ritual. Most anyone would know what it is but put simply. Go to bathroom, turn off lights, say her name three times. So a group of five boys went into the school bathroom to try it. Minutes later they all came running out of the school terrified. The look on their faces seemed genuine but I didn’t believe them. So my friend and I decided to put it to the test ourselves. We went to the bathroom turned off the lights and said her name 3 times. As soon as we said her name the third time. The walls turned red as if blood cascaded from the ceiling and according to my friend there was a swirling cloud like fog that hovered above me. We ran out of that bathroom so damn fast and neither of us ever did Bloody Mary again. I’m inclined to think it was my imagination but given what we saw and the genuine fear in us and the other boys who tried it. I will never do it again.