Day of the Dragon
The Dark Portal was created by a joint effort between the mage Medivh, possessed by the Demon Sargeras, and the warlocks of the Horde, which allowed the Horde to invade the world of Azeroth. The Portal bridged the distance between the worlds of Azeroth and Draenor, and it was large enough that individuals might pass through it. The Horde Necromancer Gul'dan immediately dispatched orc scouts through the Portal in preparation for the coming invasion. After the Portal was widened, the armies of the orcs poured through it into the unsuspecting Kingdom of Stormwind, beginning the [[First War]].