"Long ago on Draenor, the Temple of Karabor was the center of draenei worship. But the devout priests who prayed there are long dead, slaughtered by marauding, demonically corrupted orcs. In the massacre's aftermath the warlocks of the Shadow Council seized the structure and bestowed upon it a new name: the Black Temple."
Blizzard has just released a preview video of the Black Temple coming in patch 2.1. The video includes a little background story of the temple. It's very well put together and definitely worth checking out.
Curse Streaming Version
