You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within 5 feet of you. The blade charges with raw arcane energy and begins to glow before you strike. On a hit, the target suffers the normal weapon effects, damage, and in addition, takes 4d6 Force damage. 
At higher levels: When casting this spell with a spell slot above 3rd, Wrathful blade deals an extra 1d6 Force damage per level above 3rd (i.e 4th level spell slot= 5d6, 5th level slot 6d6, etc).