Cataclysm returns players to the two continents of Azeroth for most of their campaigning, after years away in Outland and Northrend. New zones opened such as Mount Hyjal, the sunken world of Vashj'ir, Deepholm, Uldum and the Twilight Highlands. It includes two new playable races: the worgen from the legendary kingdom of Gilneas for the Alliance, and the goblins of the Bilgewater Cartel from the isle of Kezan for the Horde. Flying mounts are usable in Kalimdor and Eastern Kingdoms, and the new secondary profession Archaeology is introduced.

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 more than two decades earlier, 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 worldwide disaster comes renewed conflict between the Alliance and the Horde, which is now under the rule of Garrosh Hellscream. With the elemental realms now open to the world, chaotic elemental spirits and their tyrannical lords emerged to help the Destroyer and the nihilistic Twilight's Hammer cult bring about the Hour of Twilight: the end of all life on Azeroth. 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. Looking for ways to gather more resources and new territory for his people, Hellscream has initiated several brutal strikes against the Alliance, using the cataclysm to the Horde's advantage. The human king Varian Wrynn deployed many of his forces to fight against Garrosh's aggression, storming the Southern Barrens and Stonetalon Mountains, while Garrosh, unlike Thrall, embraced war with the Alliance. There are several new areas that players can explore, along with new quests and end-scenes that players can participate in. Rise of the Zandalari Alarmed by the terrible losses of life among all trolls, the Zandalari tribe traveled around the world to reunite their race and rebuild their once-powerful empire. The Zandalari restored the fallen cities of Zul'Gurub and Zul'Aman, and begun to conduct bloody raids on territories that had once been "theirs. " The burgeoning troll force hoped to lead a great war against the other races of Azeroth, but the honorable Vol'jin of the Darkspear tribe stood against their murderous agenda, and recruited champions from both the Horde and the Alliance to invade the ancient cities and stop the onslaught. Rage of the Firelands 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. Hour of Twilight At the peak of his insanity, Deathwing the Destroyer fought to drive the world into twilight—a devastated future bereft of all life. The Dragon Soul, a powerful artifact lost in the past, was the only weapon capable of truly stopping Deathwing, and so the guardians of Azeroth—the Dragon Aspects—sent a number of valiant heroes racing through time to retrieve it. Despite being attacked by the mysterious Infinite Dragonflight as they travelled the timeways, the champions returned the artifact to the present and delivered it to the wise shaman Thrall. With his aid, the Dragon Soul was deployed against the Destroyer during a brutal battle that began in Azeroth's skies and continued into the roiling heart of the Maelstrom at the center of the world. Through the combined efforts of the Aspects and their allies, the madness of Deathwing was finally brought to an end. However, the remaining Aspects are forced to sacrifice their powers to fuel the Dragon Soul, but feel that their time as guardians of Azeroth has passed and that the heroes of the Alliance and the Horde have proved themselves ready and capable of protecting Azeroth.