Thicket of Blades

You maintain a careful guard as you search for any
gaps in your opponent's awareness. Even the slightest
move provokes a stinging counter from you.
While you are in this stance, any opponent you threaten that takes any sort of movement,
including a 5-foot step, provokes an attack of opportunity from you. Your foes provoke this
attack before leaving the area you threaten.
The Tumble skill or Withdraw action cannot be
used to avoid the attack of opportunity.