Blood Hex

You mark a target creature in range with Blood hex to increase the damage of the next attack against it. The target creature must make a Wisdom saving throw or it gains vulnerability to the damage from the next attack or spell that deals damage to it. If your attack hit you take two of your hit dice plus your Wisdom modifier as necrotic damage

If the creature has resistance or immunity to that damage type, ignore that instance of damage resistance and the creature takes normal damage.