@The Burning Legion is an infinite, world-consuming army of demons dedicated to the absolute annihilation of all life in the cosmos. Its creator and supreme master is Sargeras, a fallen Titan who was once the champion of the Pantheon. For eons, Sargeras traversed the universe, slaying the chaotic entities of the Void and imprisoning demons. However, upon discovering the existence of the Void Lords and realizing their plot to corrupt a developing Titan world-soul into a monument of unspeakable evil, despair fractured his mind.
Sargeras concluded that life was a fundamental flaw in the universe, a vector through which the Void could corrupt reality. He decided that the only way to save the cosmos from the Void was to burn it to the ground, purging all mortal civilizations so that life could never be corrupted. To achieve this "Burning Crusade," Sargeras shattered his former demonic prison, bending the chaotic, fel-wielding creatures to his absolute, titanic will.
While Sargeras possessed the raw, world-shattering power of a god, the early Legion lacked tactical intellect and organization. This changed roughly twenty-five thousand years ago when Sargeras discovered the world of Argus, home to the eredar—a highly advanced, magically gifted race. Appearing to them as a benevolent entity, Sargeras offered them untold power and knowledge in exchange for their allegiance.
While Velen saw through the illusion and fled, the other two leaders of the eredar triumvirate eagerly accepted:
Kil'jaeden the Deceiver: Appointed as the supreme commander of the Legion's strategy, Kil'jaeden was tasked with using espionage, manipulation, and psychological warfare to subvert mortal worlds from within before the armies even arrived.
Archimonde the Defiler: Appointed as the field marshal of the Legion's military might, Archimonde oversaw the direct orchestration of planetary invasions, leading the brute martial forces of the demons with devastating, ruthless military precision.
With the eredar transformed into demonic overlords, they organized the chaotic hordes of Pit Lords, Doomguards, Felhunters, and Succubi into a terrifying, highly disciplined war machine.
The Burning Legion first noticed Azeroth ten thousand years ago, drawn by Queen Azshara’s reckless over-use of the arcane energies within the Well of Eternity. Recognizing a world-soul of immense potential, Sargeras manipulated the Highborne into opening a massive dimensional portal within the lake. The resulting War of the Ancients devastated Kalimdor, but through a desperate alliance of the @Night Elf, dragon, and human races, the portal was destabilized. The Well of Eternity imploded, shattering the continent and throwing the Legion's main forces back into the Twisting Nether.
Thwarted but patient, Kil'jaeden devised a new, indirect method to breach Azeroth's defenses. On the world of Draenor, he manipulated the shamanistic @Orc clans, corrupting them with the blood of the pit lord Mannoroth to forge the bloodthirsty Horde. Under the demonic influence, the orcs slaughtered the @Draenei and constructed @The Dark Portal (Outland) , invading Azeroth in the First and Second Wars. Though the Horde ultimately failed to conquer the world for their demonic masters, the chaos they sowed severely weakened Azeroth's kingdoms.
Following the Horde's defeat, Kil'jaeden enacted a new plan that eliminated the variable of mortal free will: the creation of @The Scourge . He tortured the rebellious orc shaman Ner'zhul, transforming him into the psychic entity known as the Lich King, and cast him down onto the frozen continent of Northrend. The resulting undead plague decimated the northern human kingdom of Lordaeron and the @Blood Elf @Kingdom of Quel'Thalas , creating a massive army of mindless, loyal soldiers.
@The Scourge successfully cleared the path for the Legion's second grand invasion. Utilizing the immense arcane power of the High Elven Sunwell, the corrupted @Arthas Menethil and the fiendish @Kel'Thuzad summoned Archimonde himself into Azeroth. The Defiler marched upon Mount Hyjal to drain the energies of the World Tree, Nordrassil, which would grant him the power to shatter the planet. However, the mortal races of the Horde, Alliance, and Kaldorei formed a desperate coalition. At the climax of the battle, @Malfurion Stormrage unleashed the ancestral spirits of the forest, sacrificing the tree's immortality to vaporize Archimonde in a cataclysmic explosion.
Following Archimonde's dramatic demise and the sudden rebellion of the Lich King, @The Burning Legion found itself temporarily fractured on Azeroth, prompting them to refocus their efforts on Outland—the shattered, floating remnants of Draenor. Using @Outland as a strategic nexus, the Legion, led locally by the pit lord Magtheridon, intended to use its numerous dimensional portals to launch invasions across dozens of other vulnerable worlds.
This stronghold was temporarily disrupted when @Illidan Stormrage , fleeing the wrath of Kil'jaeden after failing to destroy the Frozen Throne, arrived with his @Naga and @Blood Elf allies. @Illidan Stormrage overthrew Magtheridon, sealing the portals and claiming @The Black Temple for @The Illidari . Infuriated by this betrayal, the @The Burning Legion launched a massive, prolonged counter-offensive to reclaim the broken world, constructing massive Legion Hold bases across the Shadowmoon Valley and Hellfire Peninsula.