Crushing Vise p. 82
The overwhelming power behind your attack leaves your opponent unable to move. The punishing strike forces it to waste a few moments shrugging off the effects of your attack.
By making a powerful, focused blow, you leave your opponent unable to move. The crushing weight of your attack forces it to waste a precious moment regaining its footing.
As part of this maneuver, you make a melee attack. This attack deals an extra 4d6 points of damage. If the creature you hit is standing on the ground, your attack also drops the target's speed to 0 feet (for all movement types) for 1 round. It can act normally in all other ways.
This maneuver functions only against opponents standing on the ground. A flying creature or a levitating target is immune to the speed reducing effect, but not to the extra damage.