I don’t remember the belief part or the cave but that’s totally possible.
I’m just gonna order like $100 of early 90s kids horror anthologies and see if I can find it. This story would be from some shit I probably got at a scholastic book fair in 1992.
There are a few more stories I remember but am not 100% sure are from the same volume:
1) a kid plays a d&d type video game and he sees it in his dreams(?) but it’s real?
2) some kids are camping in the woods and they fight or escape aliens. At the end the main kid looks at the stars and realizes they’re coming closer, the aliens are going to invade
3) some kind of story where a kid sees a monster in the mirror and the monster in his reality sees the kid in the mirror. In the end I think the human kid dies at the hand of the monster and the monster kid is scared and comforted by his monster mom?
I believe the stories I’m looking for are in an anthology by Bruce Coville, one of these:
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