Fathomdark Amulet

Black stone cut in a lozenge and hung on a short chain, cold enough underneath to print a pale mark on the skin it rests against.

Each charge fills a 30-foot radius with the pressure and quiet of deep water for one minute: no sound leaves it, no light enters it, and nothing inside can be found by scent, tremor, or magic that seeks living things. The pale mark on the skin sets permanently when depleted, and sound still fails within a foot of it.