The fantasy setting of the Warcraft series includes many fictional races and factions. Most of the primary protagonists of the series belong to either the Horde or the Alliance, however there are a variety of neutral races and factions, who either friendly or hostile to both the Horde and the Alliance. By the time of Warcraft III the Horde and the Alliance both fight against the Burning Legion and the Undead Scourge, who are the primary villains of Warcraft III and World of Warcraft. By the time of World of Warcraft, the Alliance and the Horde are not engaged in all out war any longer, however they still are hostile towards each other and skirmishes between the two sides occasionally erupt.
The Alliance has been present in some form in all Warcraft games. In all three real-time strategy games, the Alliance are the protagonists of their campaign, and are one of the two main protagonist factions in World of Warcraft. They are also the primary antagonists of Warcraft and Warcraft II's orc campagins.
Humans were introduced in Warcraft: Orcs & Humans. Throughout the first two Warcraft games, the human race was depicted as the archetypical medieval European kingdom. In Warcraft and Warcraft II they were also depicted as the protagonists of the human campaigns and the antagonists of the orc campaigns; the Humans fought for the side of Heaven against the Hellish Orcs, though this theme was abandoned in the third game.
Warcraft II introduced the human nation of Lordaeron, the nation which is depicted in Warcraft III as the main protagonists of the human campaign. The nation is exposed to a plague of undeath which turns those infected into undead monsters who serve the will of the Lich King. The prince of Lordaeron, Arthas Menethil, also eventually succumbs to the will of the Lich King and is instrumental in bringing about the downfall of his kingdom and, eventually, the invasion of the Burning Legion. He is one of the main characters of the third game and its expansion.
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