I see the vision. An excellent idea! A dare leading into curiosity/exploration is a great start to leading to this big thing. A teenager would also serve as a decent protagonist as they would be dumb enough to possibly attack some beasts rather than run. This would lead into the more RPG aspect.

There are many directions to take it. A murderer as you suggestion in an original concept could just be in the wrong place trying to hide. Perhaps an urban explorer looking around a place that hasn't seen light in many years. Perhaps a dare? The party could have other humans or even be mascots.

Oh wow! This is nice! I feel making it quirky and not too serious is the way to go. One of the ideas I thought up was just characters commentating on the silent protagonist being silent and it gets to a point where they are just like, "Oh that's just they are."

ITS NOT EVEN BEEN A DAY AND I ALREADY HAVE IDEAS IN MIND AND ACTUALLY STARTED TO CONSIDER IT SEND HELP WHAT THE FUCK

Same. It's kinda like how breathing is easy to forget about.