Blood Curse of Mutual Suffering.

As a bonus action, you can link to a creature within 30 feet for up to a minute, forcing them to share in the pain they inflict upon you. The next time the cursed creature damages you with a weapon attack, this curse deals necrotic damage to the cursed creature equal to half of the damage you suffered. This curse then ends.   Amplify. This curse instead deals damage equal the damage you suffered, and it ignores Necrotic resistance.