Gas Mine:

A Keeper invention, gas mines contain an elemental crystal. The devices within the mine rupture the crystal when activated, thereby emitting a powerful cloud of gas which usually affects all beings within the area. The procedures for aiming and activating a gas mine are identical to those of the ordinary mine. Victims must step on or near the mine to activate it. A loud hissing noise can be heard as the crystal ruptures, which may alert nearby guards.