Azeroth is the name of the primary world in World of Warcraft. Several thousand years before, Azeroth was ruled over by the four Elemental Lords: Neptulon the Tidehunter, Ragnaros the Firelord, Therazane the Stonemother, and Al'akir the Windlord. However, Y'Shaarj, C'Thun, Yogg-Saron, and N'Zoth, four powerful Old Gods, soon arrived on the planet and embedded their tentacles deep within it. A massive war ensued between the Elemental Lords and the Old Gods, with the Old Gods ultimately emerging victorious and enslaving the Elemental Lords. Eventually, the Titans of the Pantheon found Azeroth and decided to bring order to it. Aman'Thul, the leader of the Pantheon, ripped Y'Shaarj out of the ground and killed him. However, chunks of Y'Shaarj fell back to the surface, creating the sha, and the Titans created the Well of Eternity to cover the gaping hole left where Y'Shaarj once was. A great war was then fought, which resulted in a victory for the Titans and the ordering of Azeroth. They created the Elemental Plane to imprison the Elemental Lords, and imprisoned the three remaining Old Gods beneath Azeroth's surface. Civilizations began to form, with some of the titan-forged dwarves, gnomes, and vrykul being afflicted with the Old Gods' curse of flesh and becoming mortal, while other new species such as the tauren, trolls, and pandaren formed. Other new species evolved, trolls near the Well of Eternity becoming night elves, and some vrykul eventually becoming humans. Azeroth remained in relative peace for hundreds of years, but when the night elves began to practice with arcane magics, it drew the attention of the dreaded Burning Legion, who had taken over and destroyed many countless worlds throughout the Great Dark Beyond, as well as killed the entire Pantheon. This led to them invading Azeroth with the aid of Queen Azshara, which also resulted in the War of the Ancients. The Well of Eternity eventually collapsed on itself when Sargeras attempted to step through, causing Azeroth, which was one landmass at the time, to shatter in what is called the Great Sundering, causing rushing waters to submerge many new islands and continents, although many also survived, such as the Eastern Kingdoms, the landmass that is now Kalimdor, Northrend, and Pandaria, which Emperor Shaohao had separated from the rest of Kalimdor before the Sundering. After the Sundering, the Maelstrom was created in the center of the Great Sea where the Well of Eternity once was, which is a swirling whirlpool leading into Deepholm, the part of the Elemental Plane where Therazane was located.
The Burning Legion once again invaded Azeroth during the Third War, which resulted in an Azerothian victory at the Battle of Mount Hyjal when Archimonde was banished from Azeroth. Afterwards, the Lich King, Arthas Menethil, launched many attacks on the Horde and Alliance cities, and this also led up to the war against the Scourge in Northrend. After the Lich King's death, and Bolvar Fordragon was crowned the new Lich King by Tirion Fordring, the Cataclysm occurred when Deathwing blasted his way out of Deepholm, after Huln Highmountain had banished him there thousands of years before with the Hammer of Khaz'goroth. This reshaped the face of the world by creating earthquakes, volcanoes, and floods. Throughout most of this time, the Alliance and Horde were constantly at war, and they eventually discovered Pandaria, which had been shrouded in mists ever since the Sundering. Eventually, Garrosh Hellscream, the Warchief of the Horde, attempted to use the long buried powers of Y'Shaarj to conquer Azeroth with his True Horde, causing many in the Horde to form the Darkspear Rebellion, led by Vol'jin, and alongside the Alliance mount a siege on Orgrimmar. Garrosh was defeated, and Vol'jin became the new Warchief of the Horde, with Varian Wrynn, High King of the Alliance, agreeing to make peace with the Horde. Later, Garrosh escaped to an alternate reality Draenor and attempted to invade Azeroth through the Dark Portal with his new Iron Horde, however the Iron Horde was quickly pushed back.
After the Draenor Campaign on the alternate universe Draenor, the Burning Legion launched their third invasion on Azeroth with the help of Gul'dan from that alternative universe. The invasion was its biggest to date, dwarfing even the War of the Ancients. The Legion used the Tomb of Sargeras on the Broken Isles as their main portal, the isles becoming the primary setting for the invasion, although parts of the Eastern Kingdoms, Kalimdor, Pandaria, and other areas were invaded as well. The invasion shook both the Alliance and Horde, with their leaders, High King Varian Wrynn and Warchief Vol'jin, both dying as a result of the Battle of the Broken Shore. Sylvanas Windrunner became the new Warchief of the Horde, while Anduin Wrynn, Varian's son, became the new High King of the Alliance. After a war in the Broken Isles, the forces of Azeroth managed to push the Burning Legion back through the Tomb of Sargeras, and took the fight to the Legion's capital world of Argus.