Ball Lightning

You hurl a flying, crackling orb of lightning that grows in power and size as it travels towards a target you select within 120 feet of you. The orb is created in an empty space adjacent to you and is a 1-foot diameter sphere. At the end of each of your turns the orb moves 40 feet towards its intended target and grows slightly to a maximum size of a 5-foot diameter sphere. While moving, the orb will avoid hitting obstacles (unintended targets/terrain) when possible but in all other cases will move directly towards its intended target until some creature or terrain is in the same space as it. If there is no path the orb can take to avoid obstacles while approaching the target it will take the shortest path available attempting to go through the obstacle. When the orb enters the space of a target or terrain, the orb explodes, dealing 2d8 lightning damage to each target in the orb’s space. This damage is increased by 1d8 for each 10 feet the orb has moved since it was cast to a maximum of 10d8. 

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the initial damage of the spell increases by 1d8, and the maximum damage of the spell increases by 2d8 per spell slot level beyond 3rd level.