Dismember

As a reaction, after an Ally uses a melee attack against a target, You project an illusion into the mind of the target that makes them believe one of their appendages has been cut off by the Ally. The target must succeed on a Wisdom saving throw or become frightened of the Ally for the duration.

While frightened by this spell, a creature must take the Dash action and move away from the Ally by the safest available route on each of its turns, unless there is nowhere to move. If the creature ends its turn in a location where it doesn't have line of on your ally,The  frightened target can repeat the saving throw at the end of each of its turns, On a successful save, the spell ends for that creature.