Blood in the Water p. 86
The smell of blood drives you into a fury. As you slash into your foe, each fresh wound you inflict spurs you onward.
While you are in this stance, you whip yourself into a terrible rage. When you score a critical hit against an opponent, you enter a near frenzied state from the sight and smell of blood. You gain a +1 bonus on attack rolls and damage rolls. Because this is an untyped bonus, it stacks with each successful critical hit you score.
If you go more than one minute without achieving a critical hit, the stance ends and the bonus disappears.