Warforged Seal

Warforged Seals are currency used for Bonus Rolls like Elder Charm of Good Fortune, except these only work for the Siege of Orgrimmar raid and world bosses introduced in patch 5.4.0.

Source
This currency is rewarded from Warforged Seals.

Bonus rolls
The runes will only work on raid bosses added in Patch 5.4.0: all bosses in the Siege of Orgrimmar and those on the Timeless Isle.

The use of a Warforged Seal is strictly a personal endeavor and will not interfere with any other player's loot roll. It creates a completely separate roll against the boss's loot table. Most of the time, the reward is gold, but there is a chance to win an item from the boss's loot table appropriate for the player's class and role.

As in the previous tier of raids, players may use as many seals as they desire on repeated attempts of bosses in the Raid Finder mode of Siege of Orgrimmar. Players are only allowed a single roll for the Timeless Isle bosses each week. Since players may only defeat normal and heroic mode raid bosses once per week, they can only use one roll per raid boss per week