Arcane Arrow

The spell caster makes the somatic gesture of drawing back a bow, conjuring a bolt of force shaped like an arrowhead. Make a ranged spell attack against the target. On a hit, it takes 1d8 magical piercing damage.  On a critical hit (natural 20), roll an extra 1d8 and add it to the critical damage total.

This spell's damage increases by 1d8 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8).