The Lunar Dial of the Eyeless Face

The air in this windowless sanctum is unnaturally chilly and smells of burnt sage. At the room's center, a massive circular stone trapdoor is flush with the floor, radiating a soft, pulsing silver glow that defies the pitch-black new moon night outside. Four concentric stone rings encircle a central carving of an eyeless, expressionless face. Each ring is etched with various crescent and circular symbols that look like different phases of the moon. As you approach, the floor vibrates slightly, and the rings give off a faint, metallic hum that fluctuates in pitch.