Oshu'gun, orcish for "Mountain of Spirits", is located in southwestern Nagrand. It is a great, white monolith that dominates the landscape, but instead of being jagged and irregular like other mountains, it is smooth and triangular - it is said to be the largest diamond in the known universe by Gezhe. It is currently being harvested by a faction of ethereals opposed to the Consortium.
In reality, however, Oshu'gun is a naaru Dimensional Ship known as the Genedar, and was 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. Deep within the massive crystal dwells the naaru K'ure, accompanied by ancient orc ancestors, the spirits of orcs who have passed on. The Genedar is invariably linked to K'ure. Around the time it 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. It was the center of orcish culture in Nagrand until the clans became the Orcish Horde. At this point the spirits of Oshu'gun fell silent and the ancestors turned their backs upon the orcs.
As mentioned by a , K'ure was weakened by the Genedar's crash and has been trapped within the ship for centuries. As his holy energies bled away over time, 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. Recently, the Burning Legion has harnessed this vortex in order to draw countless voidspawn to increase their own ranks.
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. Rather than residing within the ship portion of the mountain, K'ure occupied a small pool of water within the crystal itself. During the Orcish festival of Kosh'harg, shaman would enter Oshu'gun and add blessed water to this pool as a ritual to speak with their ancestors. Unknown to those shaman was the fact that the blessed water also helped to sustain K'ure by allowing him to heal himself enough to slow down his dying process. With the help of its energies, the ancient orc ancestors could communicate with living shaman via dreams and visions. According to the novel, after the clans on Draenor became corrupted, these ancestral spirits did not actually abandon the living (though they did spurn the shaman who had betrayed them) nor become consumed by a dark void. Instead, Kil'jaeden and Gul'dan had a demonic barrier/guard put around the mountain which cut off the spirits and K'ure from the outside world.
Another naaru, D'ore, was all but killed in the crash of the Genedar. His remains were laid to rest by Velen and the draenei in the first crypt of what would become Auchindoun. In the intervening centuries, he has slowly been regenerating. The pull of his void energy as D'ore lay dormant is what brought the curse to Auchindoun. The same thing is now happening with K'ure at Oshu'gun.
The Burning Crusade
This section concerns content exclusive to The Burning Crusade.
At present, Oshu'gun is populated by agents of the Shadow Council from the nearby Kil'sorrow Fortress. These include terrorfiends (a subspecies of doomguard), warlocks torturing the spirits of orc ancestors, and a shivarra along with her warlocks draining the naaru K'ure at the center.
The Consortium, a group of interstellar traders and smugglers, were planning on harvesting Oshu'gun when word from their leader, Nexus-Prince Haramad, brought the operation to a halt. The nexus-prince mentioned "political situations" in Netherstorm.
It seems the Consortium does not wish to upset the naaru. 
Warlords of Draenor
This section concerns content exclusive to Warlords of Draenor.
- The former placeholder name for the ship was The Genessar.
- ^ Ask CDev Round 4
- ^ "Nexus Prince Haramad has ordered us to not begin work inside of Oshu'gun as it might anger a certain powerful naaru."
- ^ https://twitter.com/Loreology/status/412623046680145920