Iron Guard's Glare p. 59
With a quick snarl and a glare that would stop a charging barbarian in his tracks, you spoil an opponent’s attack. Rather than strike his original target, your enemy turns his attention toward you.
While you are in this stance, any opponent that you threaten takes a -4 penalty on attack rolls against your allies. This penalty does not apply to attacks made against you. Enemies you threaten become aware of the consequences of the stance.