The Three Lights of Vhal Tor

You enter a round observatory chamber where cold blue light spills from a domed ceiling painted with unfamiliar constellations. At the center stands a black-iron console, its brass edges green with age. Three empty sockets surround a dial, while a cracked blue moonstone pulses weakly in one recess. A raven, crescent moon, and rising sun are carved into the floor beneath the console. Each pulse makes the sealed stone door shimmer, and somewhere inside the walls, a patient mechanism clicks as though waiting for an answer.