Charged Strike

You charge a melee weapon you are wielding with dramatic tension that builds up during a battle. You may release this energy whenever you hit an enemy with a melee attack to deal 1d8 bonus 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 attack, the spells energy continues to grow. The thunder damage increases by 1d8 to a maximum of 4d8 bonus damage. The spell dispels after 1 minute.