Mines, they are nice things. And Nice things shouldn't be so nice to us.
I have a suggestion for mines, how nice of me? Or Not?
Mines are prone to fungi and dampness are they not? I mean, we can't build timber piles in there for a reason. (Lets totally ignore the fact that coal clamps still work in there)
Characters should gradually build in mushroom poisoning just by breathing in the air of the mine. The deeper they go, the faster the mushroom poisoning stacks. (Dream world doesn't need to have the mushroom poisoning, that would be cruel in and of itself)
I suppose I could be more cruel as to suggest that a player who has max mushroom poisoning be prone to acquiring a disease or maybe just K.O.'ing after "XX" minutes. Disease sounds a lot more fun because why K.O. when you can just perma-die for afking in the mine? Just kidding
Berrymash Laxitive is your friend in the mine, because the mine can be a quiet and eerie place with the sound of nothing but footsteps, pickax's crashing against walls, coal clamps, ore smelters, finery forges, fireplaces...(okay so there's a lot of sound but w/e)
But the basics is if you want to enjoy yourself in the mine then you need to bring farts to the equation. P.S. Pay attention to your Black Bile!