Climactic Strike

You charge a melee weapon you are wielding with the dramatic tension that builds up during a battle. You may release this energy whenever you hit an enemy with a melee attack to deal a bonus 1d8 thunder damage. Releasing the energy in this way ends the spell. At the end of each of your turns, if you didn’t release the spell’s energy into your attack, it continues to build. The thunder damage increases by 1d8.