The Twin-Key Brass Vault

A black basalt vault door fills the end of the corridor, banded in tarnished brass and engraved with dwarf runes that run in a perfect clock circle. The air smells of old oil, cold stone, and faint ozone, and every touch leaves a greasy sheen on the metal. In the center, a silent clock face waits under a crust of dust, while hidden seams around the runes give off tiny breaths of trapped air when the ring is turned. Somewhere inside the door, gears tick once whenever the party gets closer to the right alignment.