Cremation

You attempt to ignite the very soul of your enemies, burning away their life force. Choose a creature you can see within range. That creature must make a constitution saving throw. A creature takes 4d6 fire damage and 4d6 necrotic damage on a failed save, or half as much on a successful save. If a creature is reduced to 0 hit points by this damage, it turned to ash.

An undead creature makes this saving throw with disadvantage.