You hinder your opponent’s wings, feet, knees, or another body part inhibiting its ability to move.
Benefit: Pick a movement mode used by your target (climbing, flying, swimming or walking). With a successful combat maneuver, you reduce its speed by 5 feet (to a minimum of 5 feet). A flying creature drops one maneuverability category for every 10 feet of speed it loses (to a minimum of clumsy). If it drops below its minimum forward speed while in the air (or to less than half speed, if its maneuverability is average or worse), it immediately falls and takes damage as normal. Note that this effect reduces a target’s base speed as well as its speed after accounting for armor and encumbrance.
The effects of this maneuver do not stack with other effects that reduce speed. They last until the creature makes a successful Strength or Dexterity check as a move action (DC 10+ your Strength modifier).
Normal: With the GM’s permission, you can attempt this maneuver without the use of this feat at a -20 penalty, provoking an attack of opportunity. If the attack of opportunity results in a hit, the maneuver fails.
Special: You cannot negate an opponent’s movement if it moves without the aid of obvious anatomical means, such as wings or legs. Thus, you could not negate the aerial movement of a wizard under the effects of a fly spell.