Blood Boil

Make the blood of mortals reach scalding temperatures from the inside of their bodies, or you can cast it on mortal blood that you already have in your inventory.

Does 2d8 Fire dmg plus 2d4 Necrotic DMG per turn, you can upcast this with an additional 1d4 for extra Necrotic DMG.

NPC must make a CON save, half DMG if successful, full DMG + anemia if successful

Blood boiling can causing iron deficiency anemia, if the NPC fails their CON save, they will be immobile until they can pass a CON save.