History of Warcraft (World of Warcraft Supplement)
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Azeroth is a planet with much history. The races have nearly constantly waged war with each other and the arcane users have altered the layout horribly.
For much of Azeroth's prehistory, the Old Gods ruled Azeroth along with their Elemental Lieutenants. Then the Titans came and great battles ensued — resulting in the death of one Old God and the chaining of the rest. The Titans chose several Great Aspects to guard the planet and then left.
The Troll Times
Soon the Trolls flourished from Zandalar and built great empires, most notably the Gurubashi and Amani. When the Azj'Aqir empire appeared in the west, the empires battled for supremacy. The trolls were fighting on the losing side for a majority of the war. Suddenly the tides changed and the Aqir split into the Qiraji and the Nerubians.
The night elves also appeared around that time, quickly outwitting the trolls and crafted a giant magical empire using the well at the center of the world called Well of Eternity.
The Burning Legion Invasion
The Burning Legion invaded Azeroth resulting in the War of the Ancients. At the end of this, the night elves destroyed the well causing a Great Sundering that split the ancient supercontinent of "Kalimdor" apart — creating several continents, Northrend, the Eastern Kingdoms (continents of Azeroth, Khaz Modan, and Lordaeron) and "Kalimdor".
Following the war the Night Elves were split into two groups: The Night Elves, that turned to druidic magic; and the High Elves that would not give up the arcane magic. The High Elves were banished from the night elven territory and settled in the north of Lordaeron, and created the mighty kingdom of Quel'Thalas. The Amani Empire was still a strong force here, and the two very different cultures soon clashed in what became known as The Troll Wars. In the end, the elves managed to get the support of the humans, and out of the fray came two allied races and a shattered empire.
Kil'jaeden forced the once peaceful orcs and ogres to slaughter humans, dwarves, gnomes, and elves in the First and Second Wars. The bloodthirsty orcs went lethargic when they were put in internment camps.
The Undead Plague
Angered by the Horde's failure, the Burning Legion created the Undead Scourge, which lured in Arthas, the prince of Lordaeron, to join their cause and sucking Lordaeron and Quel'thalas into war. Arthas ravaged a number of cities, including the elven city of Silvermoon and corrupted the Sunwell, and thus the High Elves. This began the Third War. After devouring Lordaeron and summoning the Burning Legion, the Scourge went to Kalimdor and helped the demons move through Ashenvale and Felwood. Under the leadership of Thrall, the orcs allied the tauren and trolls and united with the survivors of Lordaeron and the Night Elves to destroy the Burning Legion.
Illidan, having been recently freed, was convinced by Arthas to kill Tichondrius, a powerful demon, by gaining untold powers from the Skull of Gul'dan. Illidan was banished from his land but was ordered by Kil'jaeden to attack the Lich King, the leader of the Undead, since they went rogue. Illidan, with the aid of the Naga, nearly met success but were thwarted by the Blood Elves and the Night Elves seeking to reclaim Lordaeron from the Scourge and to imprison Illidan again, respectively. But Illidan also freed Sylvanas and a number of other undead. The Burning Legion also gave Balnazzar a number of undead. The Forsaken, led by Sylvanas and these Legion undead fought, while Arthas and his forces fought to save the Lich King a second time. Arthas saved and became the Lich King, while Sylvanas emerged victorious in Lordaeron. The Forsaken still fight against the Scarlet Crusade, other humans, and most importantly the Scourge there. The Forsaken, Orcs, Trolls, Tauren, and Blood Elves have formed the Horde, while the Humans, Dwarves, Gnomes, Night Elves, and Draenei have formed the Alliance. The Scourge, Horde, Alliance, Naga, and others all fight for the world or simply to survive. A faction of the blood elves joined Illidan and the portal to Outland has been opened.