Blood-Lightning Bullet

As part of the action used to cast this spell, you must make a
ranged attack with a firearm against one creature within the
spell's range, otherwise the spell fails. On a hit, the target
suffers the attack's normal effects, and blood-red lightning
leaps from the target to a different creature of your choice
that you can see within 5 feet of it. The second creature takes
lightning damage equal to your spellcasting ability modifier.
This spell's damage increases when you reach higher
levels. At 5th level, the ammunition deals an extra 1d8
lightning damage to the target, and the lightning damage to
the second creature increases to 1d8 + your spellcasting
ability modifier. Both damage rolls increase by 1d8 at 11th
level and 17th level.