Charging Blade

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. On a hit, the target suffers the weapon attack's normal effects and then becomes marked with a charging rune until the end of your next turn. The next time you hit the target with and attack roll the rune explodes dealing 1d8 lightning damage and the spell ends.

This spell's damage increases when you reach certain levels. At 5th level, the melee attack deals an extra 1d8 lightning damage to the target on a hit, and the charging rune damage increases to 2d8. Both damage rolls increase by 1d8 at 11th level (2d8 and 3d8) and again at 17th level (3d8 and 4d8).