Armor bolt

You launch a shard of energy at a creature or object within range. Make a ranged spell attack against the target. On a hit, the target takes 1d4 force damage and the target loses 1 ac until the end of your next turn.

This spell's damage increases by 1d4 when you reach 5th level (2d4) and loses 2 ac, 11th level (3d4) and loses 3 ac, and 17th level (4d4) and loses 4ac.