Blood Boil

This spell attempts to disrupt the blood in a foe's body. Choose one creature you can see within range. That creature must make a Constitution saving throw. On a failure it takes 1d4 poison damage and is poisoned  until the spell ends. Creatures without blood are immune to this spell.
At 5th level the spell deals 2d4 poison. At 11th it deals 3d4, and at 17th level it deals 4d4.