Like Wrath of the Lich King, the Cataclysm expansion offers two starting areas, in an effort to prevent the overcrowding found during the Burning Crusade's launch. The first of the two available areas is Mount Hyjal in Kalimdor.
After receiving an urgent summons from the druids in Moonglade, adjacent to Mount Hyjal, you are flown into the zone atop a member of the Green Dragonflight, when you discover Deathwing in the process of summoning our old friend and former raid boss, Ragnaros, to Hyjal.
You deliver the distressing news to Ysera, a powerful dragon who protects the world from deep within the Emerald Dream, at Nordrassil.
It's decided that the only possible course of action to counter Ragnaros is to assemble the guardians of the earth, the Ancients, for an attack before he has reached his full power. However, many of the Ancients are either imprisoned or otherwise incapacitated, so its your responsibility to travel the zone and free them. For example, the Ancient wolf spirit, Goldrinn, is being imprisoned by an evil wolf spirit that you must summon, and defeat, to free Goldrinn.
You must revive the spirit of the Ancient bird spirit, Aviana, from her death and imprisonment in the Emerald dream...
and the powerful Ancient Tortolla, must be freed from his chains.
As you progress, the spirits that you help will begin to heal the land, which is burning due to Ragnaros' forces running rampant.
Throughout the zone are portals into the Firelands, the home of Ragnaros. You enter the portals and can turn back great amounts of his forces from the inside.
Once you have assembled the Ancients, it is time to enter the Sulfuron Spire and face Ragnaros.
You assist some of the world's most powerful druids in turning back Ragnaros, but you are warned that his defeat is temporary, and that he will return eventually. This is the groundwork for the soon-to-come raid, The Firelands.