When Deathwing broke through into Azeroth, the World Pillar was shattered into three pieces, the upper, the middle and the lower. If the World Pillar is not restored, Deepholm will collapse into Azeroth, as explained in  .
The shamans of the Earthen Ring, feeling the distress of the planet, work to repair the damage Deathwing caused. Thrall gave the title of Warchief of the Horde to Garrosh Hellscream while he and other shamans like Nobundo and Muln tried to stabilize the rift within the Maelstrom, keeping Azeroth from collapsing into Deepholm. Forces of the Horde and Alliance have joined forces with the Earthen Ring to repair the World Pillar, but must battle the Twilight Hammer in Deepholm to recover the missing pieces. Rather than joining Ragnaros and Al'akir, Therazane the Stonemother chose to side with the mortals, to prevent her enemies from taking her realm, or even, its eventual collapase.
The World Pillar was eventually repaired by the Earthen Ring shamans with minimal casualties.