A century and a half ago, during the American Gold Rush, A large group of miners went deep into a cave, but unfortunately, the cave collapsed behind them.
These people spent years underground, finding vegetation and animals deep in the caverns as food. But, these plants that they eat seemed to alter their DNA faster than should be possible, turning them to walking stone creatures, with crystal ores sticking out of them in various colors, mostly red, blue, or green.
These people have now adapted and formed their own society underneath. They will wear everything and anything they like, good looking or not. They replace limbs with robotic like replacements, due to the sharp rocks and deep cavern cliffs that may cause limbs to break or shatter.
Recently, they have been trying to break out to see if they can see this outside world that their ancestors talked about. These activities still continue today, and they seem to be close to breaking out..