World of Warcraft Cataclysm - The World Reborn Trailer (Game)

World of Warcraft: Cataclysm, often referred to as Cata[citation needed], is the third expansion pack for the massively multiplayer online role-playing game (MMORPG) World of Warcraft, following the last expansion Wrath of the Lich King. It was officially announced at BlizzCon on August 21, 2009, although details were discovered earlier. The expansion was officially released on the 7th of December 2010.
Shortly after the announcement of the release date, on October 5, Blizzard implemented the overhaul of the game's playing systems (Patch '4.0.1').
Before Cataclysm was announced as the official title of the expansion, it was known internally as World of Warcraft: Worldbreaker.

text source: wikipedia.org