Doomtide

Create a 20-ft. radius sphere of inky fog and magical darkness within range. A hostile creature that enters for the first time on a turn or starts there must make a WIS save, taking 5d6 psychic damage and subtracting 1d6 from its next save before your next turn on a failed save, or half damage only on a success.

This power has its own stable page so it can be linked from any character, item, location, story post, bargain, curse, or future reward.