Broken Wing

You take an imaginary swipe at a target within range as you cast this spell. The target must make a Constitution saving throw. On a failed save, it takes [roll]2d6[/roll] slashing damage and reduces either its flying or walking speed (your choice) by 10 feet. On a success, it takes half damage and its speed is not reduced. If the target regains 5 hit points, the reduction to its speed ends. 

From the Southlands Player's Guide (Kobold Press).