As part of the cost of casting this spell, you must sacrifice a hit die or the spell fails. If you do not have a free hand to hold the whip it will also fail. If the spell succeeds, a red whip forms from your blood in your chosen hand. The Blood Whip has reach (10ft), deals 1d6 slashing damage and is considered magical. You are considered proficient with the weapon and can use your spellcasting ability modifier instead of Strength or Dexterity for the attack and damage rolls. If you take the attack action with the Blood Whip, you can only make one attack. Attacks of opportunity occur as normal. The spell ends if you cast it again or if you let go of the weapon.