The World of WarCraft changes forever with the coming of Cataclysm. The earth quakes, oceans burst forth, and well-known landscapes crack and crumble, as the ancient dragon aspect Deathwing makes his destructive return to the mortal realms. Unlike earlier WoW expansions, which add new continents for players to explore, Cataclysm reshapes the game's original world of Azeroth, permanently altering many familiar locations across the Eastern Kingdoms and Kalimdor. Some world regions become more dangerous, some are made more accessible, and some reveal forgotten treasures to challenge the game's most powerful heroes.

With this worldwide upheaval come new areas to explore, additional playable character races, and battlefields and dungeons of unprecedented danger and reward. At the expansion's December 2010 launch, this widespread transformation of Azeroth is experienced by all World of WarCraft players, but the new areas, abilities, quests, and character types are available only to those with the Cataclysm add-on. Like earlier expansion sets, Cataclysm requires full installations of the main World of WarCraft game and the previous add-on packages, Burning Crusade and Wrath of the Lich King.

Higher-level player characters now can train to use their flying mounts in the reshaped world of Azeroth, and some of the most challenging areas introduced in the expansion can only be reached on-the-wing. Cataclysm raises the character level cap to 85 and emphasizes end-game content, with extensive quest lines, heroic instances, and raids designed for top-level characters. Class abilities are refined and the talent tree systems are revamped. The expansion also adds two 15-level starting areas, one for each of the new playable races.

The wolf-like worgen of Gilneas, released from their self-imposed isolation by the destruction of the Greymane Wall, join the Alliance. A faction of goblins, forced to flee volcanic eruptions at their remote island homeland, joins the Horde. Previously unavailable combinations of existing character races and classes, such as human hunters and troll druids, also become playable in the expansion. A new secondary profession, Archeology, allows characters to uncover lore from the ancient days of Azeroth, and to earn useful rewards as they learn the skill. High-level resources and recipes are added for all the main professions, as well.