Geas

Give a verbal command to one creature that can understand you. The target must make a WIS save or become bound to carry out a service or refrain from a course of action. If it knowingly acts against the command, it takes 5d10 psychic damage once per day. The command cannot require certain death.

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