World of Warcraft: The Burning Crusade

The Doom Lord Kazzak reopened the Dark Portal to Outland, flooding Azeroth with the ravenous demons of the Burning Legion. Expeditions from the Horde and Alliance, reinforced by their new blood elf and draenei allies, passed through the gateway to stop the invasion at its source. On Outland's desiccated Hellfire Peninsula, the Alliance discovered several of their heroes who had crossed through the portal many years before, while the Horde made contact with the Mag'har - 'uncorrupted' orcs who had not participated in their race's original invasion of Azeroth. The expedition into Outland dragged Horde and Alliance armies further into conflict with the agents of the Legion and the lieutenants of Illidan Stormrage, who had claimed the shattered realm for his own.