injury penalty
As your health drops below a threshold, you will start to suffer a penalty to your skills, increasing as you get closer towards death. The threshold is determined by discipline (with 100 discipline you start taking a penalty to skill percentages once you drop below 50% hitpoints). The ashura skill as well as the kamikaze stance or going berserk (berserk, frenzy, drunken fury, shan-ya) reduce the severity of the penalty by half. Other factors can reduce your effective skill percent as well, such as being encumbered.