Eye Of Medani

The power of your dragonmark sharpens your senses.
Prerequisite: Any Mark of Detection.
Benefit: Once per day, you can reroll any one Spot check. The decision to reroll must be made before learning the outcome of the original roll, and you must accept the result of the second roll.
In addition, if you possess the lesser Mark of Detection, you reduce any miss chance you suffer against your foes by 20% (to a minimum of 0%). If you possess a greater Mark of Detection or a Siberys Mark of Detection, you instead reduce any miss chance you suffer against your foes by 50% (to a minimum of 0%).

Source: Dragonmarked