Voltaic Blade

You brandish the weapon used in the spell’s casting and make a melee attack with it. On a hit, the target suffers the attack’s normal effects and is prevented from taking reactions until the start of its next turn.

At the 5th level, the melee attack deals an extra 1d8 lightning damage, which increases to 2d8 at level 11 and to 3d8 at the 17th level.