Caught Breath

In several areas of the Shadowdark, the warm breath of living creatures freezes in the air, forming tinkling crystals. This is no mere fog. Each exhalation curls out and then halts in midair. Beards and mustaches swiftly become rimed with ice, and glinting frost collects all around the head and shoulders.
    An area of caught breath fills an encounter-sized cavern, though the icy exhalations appear to drift through the Underdark on imperceptible winds and can also be encountered in narrow tunnels or areas of much larger chambers. Caught breath can be identified with a DC 20 Dungeoneering check.

    Effect: Creatures in an area of caught breath take a -10 penalty to Stealth checks. Creatures that don’t breathe (such as angels, constructs, living constructs, and undead) do not take this penalty.
    Usage: Caught breath has a limited impact on combat, so its placement is more flavorful than dangerous. Placing it in an area where the characters have incentive to move quietly—perhaps forcing them to take a more elaborate and perhaps dangerous path—can add to the tension of a scene.

Published in Underdark, page(s) 120.