In 2007, the Dark Portal to Outland opened. As the demons of the Burning Legion flooded Azeroth, World of Warcraft grew bigger than ever before. In just 3 years, Blizzard's MMO had grown to dominate the genre and showed no signs of slowing down. World of Warcraft: The Burning Crusade represented the developer's most ambitious addition to the game yet, a full-blown expansion that soon became the fastest selling PC game released up to that point.