Charm of the Storm

You become charged with the power of the storm, to the extent that tiny sparks crackle in your eyes. You can cast the Lightning Bolt spell (3rd-level version) as an action. Once used three times, the charm vanishes from you.

A stroke of lightning forming a 100-foot-long, 5-foot-wide Line blasts out from you in a direction you choose. Each creature in the Line makes a Dexterity saving throw, taking 8d6 Lightning damage on a failed save or half as much damage on a successful one.

Using a Higher-Level Spell Slot. The damage increases by 1d6 for each spell slot level above 3.