The Echoes of Copper-Memory

You enter a circular chamber of black basalt where the air smells of hot metal and old dust. Four empty sockets interrupt a waist-high plinth, each carved with a star, an eye, a bell, or a root. Above them hangs a cracked crystal lens. Pale blue light flows through it, projecting four symbols in succession while a clear chime, a whisper, a ringing note, and a deep wooden knock sound in turn. When the display ends, the light vanishes, leaving only the faint afterimage of the sequence in your vision.