Backlash

You ward yourself against destructive energy, reducing the damage taken by 4d6 plus your spellcasting ability modifier.

If the triggering damage was from a creature within range, you can force the creature to make a Constitution saving throw. The creature takes 4d6 Force damage on a failed save or half as much damage on a successful one.

Using a Higher-Level Spell Slot

The damage reduction and Force damage from this spell both increase by 1d6 for every spell slot level above 4.