The central plot of the expansion is the return of the evil dragon aspect Deathwing the Destroyer (originally Neltharion the Earth Warder). Last seen in Warcraft II, which took place over a decade before, Deathwing has spent that time healing himself, and plotting his fiery return from the elemental plane of Deepholm. His return tears through the dimensional barrier within Azeroth, causing a sweeping cataclysm that reshapes much of the world's surface. In the midst of the world-wide disaster comes renewed conflict between the Alliance and the Horde, which is now under the rule of Garrosh Hellscream.
The Cataclysm is responsible for a number of political changes within the Horde and Alliance. With the wake of the cataclysm, the Horde's leader, the orc shaman Thrall, stepped down from his duty as Warchief of the Horde to better help the world of Azeroth as a whole. This duty was relinquished to the former overlord of the Warsong Offensive, the Mag'har orc warrior Garrosh Hellscream. The human king Varian Wrynn deployed many of his forces to prosecute the war against the Horde, storming the Southern Barrens and Stonetalon Mountains, while Garrosh, unlike Thrall, embraced war with the Alliance.
There are several new areas the players will investigate and also join in different actions by either quests or endscenes.