Shifting Defense p. 73
You duck and move as you dodge your opponent's attacks. Slowly but surely, each attack gives you the opportunity to move across the battlefield.
Your ability to read your opponents' moves and use their strength against them allows you to shift your position during a battle. Each failed attack gives you the split-second you need to move without drawing attacks.
While you are in this stance, you can make an immediate 5-foot step each time an opponent attacks you. Moving in this manner consumes one of your attacks of opportunity in the current round. You cannot move in this manner if you have no attacks of opportunity remaining. This movement does not provoke attacks of opportunity.
The 5ft step granted by this stance takes the same action it takes to make an attack of opportunity (effectively no action), not an immediate action. The 5ft step occurs before the attack is made, but after it is declared. If you are still within the attacker's melee reach after taking the 5ft step, the attack is resolved normally. If not, the attack is wasted and the attacker cannot make another melee attack against you until you are again within its melee reach.