Improved Low Blow( Races of Faerûn, p. 165)
You are especially good at using the Low Blow feat.
Using the Low Blow feat does not provoke an attack of opportunity when you move into an opponent's square to perform the attack.
A character with the Low Blow feat may enter an adjacent opponent's square to make a single attack, then return to his own square. The opponent is considered flat-footed against the attack, but the character is subject to an attack of opportunity.