Crippling Shot

Pact of the Trigger

Once per turn, when you damage an enemy with an attack made using your hex gun, you can force them to make a Strength saving throw against your spell save DC or fall prone and have their speed reduced to 0 until the start of your next turn.
You can use this ability a number of times equal to your Charisma modifier, and regain all expended uses after completing a long rest.