Arcane Spear

As a part of casting this spell make a single attack with a thrown or ranged weapon. Once the projectile is airborne it is surrounded by a spear of force energy which deals extra damage. If the attack hits it deals an extra 1d6 force damage on top of regular attack damage. In addition, the spear travels through the target hitting additional creatures up to 10ft directly behind the original target, each of these creatures receive only the additional force damage from this spell. 

This spell's damage increases by 1d6 when you reach 5th level (2d6), 11th level (3d6), and 17th level (4d6).