Almost 25,000 years ago, a faction of Eredar led by Velen fled their homeworld of Argus, calling themselves the Draenei ("the Exiled Ones"). After traveling through the cosmos they finally found a world which they called Draenor ("Exile's Refuge"). They at first shared a peaceful existence with the native Orcs and traded with them. They followed the path of the Holy Light of Creation as shown to them by the Naaru. However by coming to the planet they also lured their the Eredar there, who found the Orcs to be easily manipulated. Unfortunately, the Draenei were almost completely exterminated by the Orcs led by the warlock Gul'dan shortly after the Orcs' corruption.
After the Dark Portal was destroyed, Draenor collapsed in on itself, and what remained was a sundered mass of planetary debris and floating asteroids hovering in stasis within the Twisting Nether. The regions of Draenor that are still habitable are now known as Outland. Draenor was not the only thing to change in this ordeal, as some Draenei were altered by the destruction of their world, and became known as the Broken. Some of these corrupted Draenei fled through the open portals on Draenor and settled in the Swamp of Sorrows on the world of Azeroth. Several of these Lost Ones were driven mad by the absence of their home world, and sank into an even deeper primitive state.
A number of Draenei still remain untainted, and it is these that are destined to come crash landing onto Azeroth in a planar ship sabotaged by the malicious Blood Elves of Outland.