Umbral Mark

 
Prerequisite(s): Any Least, Lesser, Greater, Siberys Mark of Shadow
 
Benefit: Once per day you can reroll any one hide check. The decision to reroll must be made before learning the outcome of the first roll and you must take the second roll regardless. In addition, any critical hit or sneak attack made against you has a chance of being negated so that damage is instead rolled normally. The benefits of this feat do not stack with other means of reducing your critical or sneak attack percentage. The percent chance of avoiding the critical hit or sneak attack depends on the strength of your dragonmark:
 
Lesser: 25%
Greater or Siberys: 50%
 
Source: Dragonmarked