Discharge

A 5-foot-diameter sphere of lightning appears in an unoccupied space of your choice within range and lasts for the duration. The sphere has a 15 foot radius of crackling energy around it. Any creature that enters the spell’s area for the first time on a turn or starts its turn there must make a Constitution saving throw. On a failed save a creature takes 4d8 Lightning damage, and is pulled in 5-feet towards the center of the sphere. On a successful save a creature takes half as much damage and is not pulled towards the sphere. A creature pulled into the sphere takes an additional 2d10 lightning damage. 

For the duration on each of your turns, after the spell is cast. Until the spell ends, you can use your action to pulse the sphere, causing creatures inside to be pulled 5-feet towards the sphere. As a bonus action, you can move the sphere up to 30 feet to an unoccupied space.