Tether Essence

Choose two creatures with blood within range. Each must make a CON save, with disadvantage if they are within 30 ft. of each other; either can willingly fail. If both fail, they are linked for the duration regardless of distance on the same plane. Whenever one takes damage, the other takes the same damage. Whenever one regains hit points, the other regains the same amount. If either drops to 0 hit points, the effect ends on both.

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