Deep Magic Volume 2 (p.229)
Swing and a Missile
0-level (Cantrip) Evocation
Casting Time: 1 reaction, which you take when a friendly creature you can see within 30 feet of you misses an attack roll
Range/Area: 30ft.
Components: Verbal
Duration: Instant
Attack/Save: Ranged Spell Attack
Damage/Effect: Force
You take advantage of the momentary distraction an ally’s attack provides, firing a miniature arcane missile at your ally’s target just as the ally’s attack misses. Make a ranged spell attack against your ally’s target. On a hit, the target takes 1d4 force damage.
This spell’s damage increases by 1d4 when you reach 5th level (2d4), 11th level (3d4), and 17th level (4d4).
Available for: Bard, Sorcerer, Wizard