Voltaic Cloud

You create a 10-foot cube filled with a cloud of roiling electric energy centered on a point within range.

Each creature completely within the cloud at the start of its turn must make a Dexterity saving throw against lightning damage.  The creature takes 3d6 lightning damage on a failed save, or half as much damage on a successful one.

Creatures that are wearing metal armor, or wielding a metal weapon have disadvantage on this saving throw and take an additional 1d6 of lightning damage.

On your turn, as an action, you can choose to move the cloud up to 30 feet.

When you cast this spell using a spell slot of 4th level or higher the damage increases by 1d6 for each slot above 3rd level.