Clot

You unleash your virulent blood into a creature that you touch. The target must make a Constitution saving throw. On a failed save, it takes 10d6 necrotic damage, or half as much on a successful save. If the target fails the saving throw, its hit point maximum is reduced by an amount equal to the necrotic damage it took and any healing it would receive is halved for 1 hour. Any effect that removes a disease allows a creature's hit point maximum to return to normal before that time passes.