Oshu'gun, said to be the largest diamond in the known universe by Gezhe in the original timeline, is located in southwestern Nagrand. Oshu'gun is orcish for "Mountain of Spirits". It is a great, white monolith that dominates the landscape, and instead of being jagged and irregular like other mountains, it is smooth and triangular. Deep within the massive crystal dwells a naaru named K'ure, accompanied by ancient orc ancestors, the spirits of orcs who have passed on. Oshu'gun is in fact a naaru Dimensional Ship called Genedar, and was the vessel K'ure and K'ara used to help the draenei flee Argus thousands of years ago, traversing the Twisting Nether until it crash-landed on Draenor approximately two centuries before the First War.
Oshu'gun is invariably linked to K'ure. Around the time Oshu'gun landed, K'ure fell ill, rendering the ship useless.
In the time following this event, the orcs came to revere the enormous gem. It became a sacred place and every year the orcs would gather there to celebrate the spring and autumn festival. The shaman would commune with their honored ancestors (who, unknown to the shaman, came to dwell within Oshu'gun to commune with K'ure). Recognizing the orcish reverence, the draenei retreated from the mountain.
As in the original timeline, it is presumed K'ure was weakened by Oshu'gun's crash and has been trapped within the ship for centuries. As his holy energies bled away over the centuries, a void slowly grew in his place — devouring the souls of those nearby. K'ure watched helplessly as generations of orc spirits were consumed by this vortex.
The novel Rise of the Horde, which was developed prior to the expansion, presents a slightly different nuance of K'ure's relation to Oshu'gun. Most likely, though, this story may not apply to new Draenor, as it involves the participation of the Burning Legion that has not yet come to the world in Warlords of Draenor.
Unless the story changes again, another Naaru, D'ore, was all but killed in the crash of Oshu'gun. His remains should still be laid to rest by Velen and the draenei in the first crypt of what would become the alternate timeline Auchindoun. We don't know how D'ore has affected this version of Auchindoun, yet. In the Draenor version of events, there was also an additional Naaru named K'ara aboard the ship when it arrived on Draenor. However, K'ara was ejected from the ship as it descended to Draenor, becoming The Dark Star.
"I'm sending you to Nagrand to subjugate the naaru in Oshu'gun.".
Players later find Cho'gall inside the sanctum of the naaru within Osu'gun, in the midst of channeling a spell directed at K'ure. Gul'dan arrives and questions Cho'gall's actions, demanding he hand over control of the darkened Naaru. Cho'gall refuses, stating that he has learned much from K'ure, but is finished taking orders from Gul'dan. Shortly after, players witness the birth of the void god  , transformed from the remains of K'ure. Vindicator Nobundo and the player defeat Decimatus, but the sanctum begins to crumble around them, forcing them to make a hasty escape.