Amaterasu

Target four creatures/objects of your choice within sight. That creature needs to make a Dexterity saving throw or start becoming engulfed by black flames. These flames burn anything they touch including other flames, can’t be put out by water, only dispel magic or remove curse. This fire ignores fire resistance and immunities. The black flames deal 6d8 of fire damage at the beginning of the afflicted creatures’  turns. The caster can choose to put out the flames as a free action. If the afflicted creature dies while burning, they turn to ash upon death and can only be resurrected by a true resurrection or wish spell. Amaterasu burns slower than regular fire, can remove armor/clothing, or appendages to stop spread.