Choose a creature within 30 ft. of you. It must make a Constitution saving throw. On a failed save, a strand of necrotic energy creates a blood bond between you and the target. Whenever you take damage, the other creature in the blood bond takes 3d10 necrotic damage. 

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d10 for each slot level above 2nd.