Ball Lightning

Make a ranged spell attack against a creature in range. On a hit, they take 7d8 lightning damage as an orb of erratic electricity flies toward them and bursts on impact. This spell’s damage is critical when you roll an 18, 19, or 20 on the hit die.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the damage is critical when you roll a lesser number on the hit die for each slot level above 4th. For example, casting this as a 5th level spell also causes a 17 to be critical.