divine decay

You hurl a ball of a Bright glowing mist. Choose one creature you can see within range. A target must succeed on a Dexterity saving throw, on a failed save or take 3d6 necrotic damage and if applicable they lose necrotic resistance for 1 minute(apply damage after lose of necrotic resistance).  

This spell’s damage increases by 1d6 for every spell slot used above 2nd