The Threefold Frost Lock

A square dungeon chamber breathes a dry, bitter cold that makes every torch flame lean blue. At the far wall stands a black-iron vault door veined with frost, its three concentric rings ringed by pale ice sigils that glitter whenever someone speaks. The stone floor is slick with a thin skin of meltwater, and each wrong turn of the dial answers with a soft click, a hiss from the wall pipes, and a bloom of rime crawling across the metal like a warning that the door remembers every mistake.