Exacerbate

This Spell is a Rare Spell this type of spell you need to find or unlock from a spell scroll or some other Source (optional rule)

When you see a creature take piercing or slashing damage you can curse the wound causing it to bleed out. The creature Must succeed on a Constitution saving throw or take 2d4 necrotic damage at the beginning of each of its turns for the spell's duration. the creature can attempt this saving throw again by using an Action to Clean or Burn the wound

At Higher Levels. 

When you cast this spell using a spell slot of second level or higher, the damage increases by 2d4 for each spell slot above 1st level