When the draenei first came to Azeroth, they landed in spectacular fashion, tearing up an island off the coast of Kalimdor. New draenei players are taken on a journey through the wreckage and the mess, picking up the pieces and dealing with the unique effects the crash had on both flora and fauna. Several years later, and it seems the draenei are still doing clean-up work -- although that may be more due to Azuremyst being perpetually stuck in the past for mechanics purposes, rather than story content.
Why bring this up? Because it's not the first time the draenei have shattered a world. On Draenor, the new inhabitants of the planet landed in similar fashion, tearing up a great chunk of Draenor's landscape in Nagrand. Both times, the incidents were due to faulty ships -- and both times, the surrounding region was affected. But while Azeroth's torn landscape and blood-tinged skies were obvious demarcations of narrowly-avoided disaster, the landing of the Genedar was viewed as something different entirely to the natives of the world. To the orcs, it was unknown -- and then thought, perhaps, to be a gift from the ancestors.
They couldn't be further from the truth.
Please note: The following Know Your Lore contains several spoilers for Warlords of Draenor. If you are avoiding spoilers while you are leveling, come back when you've finished Nagrand.