Phantasmal Force

Choose one creature you can see within range. The target must make an INT save or perceive a phantasmal object, creature, or hazard no larger than a 10-ft. cube. The target treats it as real. Once per turn, if the target is within or adjacent to the phantasm, it takes 10 (3d6) psychic damage.

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