Prerequisite(s): Exposure to call lightning, lightning bolt, or chain lightning spell.
Benefit: Whenever you take damage from an electricity effect, you may send a line of electricity arcing from your body at any single target within 30 feet. This bolt deals half the damage you just took; a Reflex save (DC 16 + your Cha modifier) halves this damage.
Source: Unearthed Arcana