After the Horde’s defeat, the elder shaman Ner’zhul reunited the clans of Draenor. His goal differed from Gul’dan’s: he intended to open portals to other worlds and lead the orcs away from their dying home. The ritual required powerful artifacts held on Azeroth.
The orcs restored the Dark Portal and launched swift raids. In response, the Alliance sent an expedition led by Turalyon. Alleria Windrunner, Khadgar, Danath Trollbane, and Kurdran Wildhammer crossed with him. They knew that defense was not enough; the threat had to be stopped on the other side.
Ner’zhul began the spell before they could reach him. Too many dimensional rifts broke the integrity of Draenor, and the planet began to collapse. Khadgar sealed the Dark Portal from the doomed world so the catastrophe could not spread to Azeroth. The expedition remained beyond the veil, while Ner’zhul disappeared through one of his gateways.
Blizzard’s account confirms that Ner’zhul’s portals tore Draenor apart. Its remnants became Outland, while Kil’jaeden captured the fleeing shaman and prepared a new fate for him: transformation into the Lich King.
Official Blizzard source: Official World of Warcraft source