The Threefold Lock of the Drowned Moon

You enter a circular chamber of damp silver stone, where ankle-deep water ripples around a raised pedestal. Three copper dials sit within it, their glyphs catching the blue light of a bronze lantern. The air smells of salt, cold iron, and extinguished incense. A stone door fills the far wall, its seams glowing faintly whenever the dials move. Above the pedestal, a slate plaque bears a poem whose silver letters gleam like moonlight beneath the water.