Thomas's Electro Static Lightning Accumulator

This spell draws on ambient energy to store electrical charge. This can be released as a bonus action.

The spell stores a d6 at the start of your turn, it stores an additional d6 if anyone casts a spell dealing lightning that round. This can only occur once per round

As a Bonus action on your turn you can make a ranged spell attack at a target within 30ft, discharging upto your spell casting modifier of d6s lightning damage on a hit. You expend the d6s before you roll the attack.

When the spell ends any remaining d6 harmlessly dissipate.

For every level you upcast above 2nd you start with 2d6s stored (eg. Starts with 6d6 if cast a 5th level)