Extra loot rolls
Level 90 players can choose to use an [Elder Charm of Good Fortune] (for Patch 5.0 bosses), [Mogu Rune of Fate] (for Patch 5.2 bosses) or [Warforged Seal] (for Patch 5.4 bosses) for an additional roll on loot after every attempt. This second roll works just like the first roll does and will not affect in any way other players' loot.
A charm may also be used, on most bosses, for an additional roll even on subsequent kills during the same week. For example, a player may return to Lei Shi and kill her a second time, receiving no loot by default, but use a charm and get another chance. Notable exceptions include the Sha of Anger and Sha of Fear, on whom only one charm may be used per week.