When you score a critical hit with a weapon, instead of rolling double hit dice, the player deals the regular amount of damage to their target, and a mysterious stranger with a pistol appears in a place of the player's choosing (within 30 feet) and deals 1d10 to an unfriendly target of the DM's choosing. As a result, the target must roll a d4 on their next turn to determine who they attack. On a 1 or 2, they target the mysterious stranger, who immediately vanishes. Regardless of the roll, the mysterious stranger vanishes before the player's next turn.