You draw blood from your own body, either sending a bolt of blood out into an enemy or transforming it into ammunition and shooting it with a ranged weapon (using a ranged weapon overrides the spell's distance, to the first increment of the ranged weapon).
You take 4d4 necrotic damage. This can't be reduced or removed in any way. Make a ranged spell attack. The blood is taken from your body and shot into the target, dealing 4d6 magical piercing damage on impact. You then deal additional damage based off the rolls of your d4s, a 1 being 1d4, a 2 being 1d6, a 3 being 1d8, and a 4 being 1d10. You may choose to maximum a die/dice if you wish. The extra damage then deals a damage type of your choice, from acid, cold, fire, lightning, necrotic, poison, or radiant. The different die may be the same damage type or a different damage type. If you miss with your attack, the blood returns to your body and you gain back the damage you had taken.
If the target is concentrating on something, they lose concentration. If the concentration is on a spell, the target also takes 2d6 psychic damage as the volatile magic rips apart the target's connection to their magic.
For every spell level this spell is cast above 4th, the initial piercing damage increases by 1d6.
* - (One ounce of fresh blood drawn from an open wound on your body)