Deathwing and the Shattering

Deathwing the Destroyer - once Neltharion, the black Dragon Aspect meant to guard the earth, long ago driven insane by the Old Gods - erupted from the world's core. His emergence, the Shattering, tore open zones across Azeroth and reshaped the map players had known for years.

The other Dragon Aspects, their powers fading, made a final stand against him. To land the killing blow they poured the last of their draconic might into a weapon, ending Deathwing but also ending the age of the all-powerful dragonflights - a sacrifice that echoes for expansions to come.