Patch 4.2.0: Rage of the Firelands contains the Firelands raid, and is the end of Arena season 9. It has also added a daily quest hub to Hyjal, as well as two new daily quest zones called the Regrowth and the Molten Front. It will continue Thrall's story. It has also introduced the new Dungeon Journal feature.
After a ferocious series of battles, Azeroth's heroes banished Ragnaros the Firelord and his elemental minions from Mount Hyjal. Yet, threats to Hyjal persisted, including traitorous druids who had abandoned their allies and joined forces with the elementals. Fearing another elemental invasion, the defenders of Azeroth made a daring assault into Ragnaros' blazing realm: the Firelands. Among the seething flames of this elemental domain, Ragnaros was at his most powerful; only the greatest champions of the Horde and the Alliance, aided by druidic champions like Malfurion Stormrage, could dare hope to defeat the Firelord.