The Covenant of River, Flame, and Stone

A circular chamber of dressed stone lies beneath a soot-black dome, its walls banded with three slate tablets and its center dominated by a waist-high pedestal with rotating rings of bronze, iron, and jade. The air smells of wet rock, old incense, and a faint electric bite. When any ring turns, the basin at the pedestal's foot pulses with colored light, blue for wrong alignments and gold for near-correct ones, while the central iron mask clicks softly as though holding its breath.