Delayed Cataclysm

Prepare a powerful delayed reaction in a structure, battlefield, vehicle, machine, vault, road, or object no larger than a 60-ft. cube. Choose a trigger. When triggered, creatures in the area must make a DEX save, taking 8d10 fire, acid, thunder, or force damage on a failed save, or half on a success. The effect is obvious to careful inspection unless hidden with an appropriate check.