Divine Blade

A blade of pure divine energy forms in your hands. This magic sword lasts until the spell ends, leave your hands, or is dismissed (requires no action). It counts as a martial melee weapon with which you are proficient, and has the finesse property.

You may use your action to make a single melee attack with the divine blade. On a hit, the target takes 1d8 radiant damage, and until the start of your next turn, the next creature to make an attack against the target can roll a d4 and add the number rolled to the attack roll. 

This spells damage increases by 1d8 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8).