Gives a chance of significantly increasing the damage from the impale skill.
The in game help reads:
Skill duration: random. Type of skill : neutral skill. Affecting stats: Str/Dex. It uses no endurance points. While impaling an opponent is a difficult task, those who can execute this maneuver with ease can sometimes having once impaled their foe, twist their weapon so it rips and tears the victim, until the weapon is pulled completely out of their victim. Once this is done, another impaling maneuver can be done, before the victim has time to react.