The Violet Ruin Opening

You enter a circular vault where violet light leaks through cracks in the walls like moonlight beneath deep water. In the center stands a waist-high square frame of black stone, filled with pale stone plates marked by dark-purple lines. The image is almost recognizable as a ruined temple, but its pieces are scrambled around one empty space. Every few breaths, a low hum passes through the floor, and the purple lines flicker toward the empty space as if waiting for the ruin to be rebuilt.