When he touched the wall, it didn't feel like hardened soil, it felt like stone. Perhaps the room had been carved directly out of rock.
Both the walls and ceiling were made of black stone that glistened faintly with a smooth glossy layer. It looked very similar to the black agate stones he had seen earlier at the merchant's stall in the village square.
It must be a vein of those black stones.
"It's a rare stone that can only be mined deep inside the mountains," the merchant had said.
If that was true, then was this place actually underground? Seeing the layers of stone surrounding him, it seemed certain he was right in the middle of the mineral vein itself.
Thinking back over everything that had happened, if no device was being used, then the reason his psychic power was being suppressed had to be this black stone.
