Dark Matter Grenade

You conjure up a ball of swirling dark matter in your hand. You throw it within range and all creatures within a 20ft radius must make a dexterity saving throw or take 3d10 necrotic and 3d10 explosive damage. On a failed save creatures take half damage. Any creature who stays in this void takes 1d6 damage. When you expend a spell slot of 5th level and above the number of d6s goes up by 1.