Blood Bomb

You rip a vein or artery from your body, infuse it with dark magic and throw it to a point within range. The vein erupts in an explosion of blood and gore. Each creature in a 15-foot-radius sphere centred on that point must make a Constitution Saving Throw. A target takes 6d6+6 necrotic damage and takes one level of exhaustion on a failed save, or half as much damage on a successful one and is not exhausted. 

The blood leaves a patch of viscera on the ground, making it difficult terrain until it is washed away.

Your maximum hit points are reduced by 6 times the spell level used to cast the spell.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 2d6 for each slot level above 3rd.