Thundershock

A small lighting bolt arcs from your hand. Make a ranged spell attack. On a hit the target takes 1d6 lightning damage. If the target is missing any of its hit points, the thunder created from the bolt reverberates through their wounds and they suffer an additional 1d4 thunder damage.

The spells damage increases by one die for for each damage type when you reach 5th level (2d6 and 2d4), 11th (3d6 and 3d4), and 17th (4d6 and 4d4).