Voltaic Cloud

Call forth a 10ft radius sphere of dark clouds and crackling bolts at a point you can see within range. Each creature that enters the space or starts its turn there must succeed on a Dexterity saving throw or take 1d8 lightning damage and 1d8 thunder damage or half damage on a successful save. On subsequent turns, you can use your bonus action to move the cloud 15 feet so long as you maintain concentration

When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d8 lightning and 1d8 thunder for each slot level above 2nd.