Unleashed Blade

As part of this spell's casting, make a melee attack with a bladed weapon against a target within range.  On a hit, the weapon is destroyed, and the target takes damage equal to 3 times the weapon's damage dice. (A shortsword does 3d6, a longsword does 3d8/10, a greatsword does 6d6, and so on)

at higher levels.  When this spell is cast at 3rd level or higher, add another multiplier of the damage dice.