Massacre [two-actions] Spell 9

You unleash a wave of death to snuff out the life force of those in its path. Each living creature of 17th level or lower in the line must attempt a Fortitude save. If the damage from massacre reduces a creature to 0 Hit Points, that creature dies instantly. If massacre doesn't kill even a single creature, the void energy hungrily turns backward toward you, dealing an additional 30 void damage to every living creature in the line (even those above 17th level) and 30 void damage to you.