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When Deathwing briefly relocated to Draenor in the aftermath of the Second War, the great black dragon built a new lair, Deathwing's Lair, on a rocky island a short flight east of Hellfire Peninsula and the Skeletal Coast. It served as the headquarters of Deathwing and the other dragons allied with the Horde during the Dark Portal Crisis after the Second War. However, Deathwing made a tactical error in capturing Kurdran and Sky'ree, as this brought the wrath of Archmage Khadgar and Alleria Windrunner upon him. The pair freed Kurdran, who proceeded to raze the Lair to the ground.
Deathwing was originally reported killed in the battle, but in fact had returned to Azeroth. He left behind a clutch of eggs in his lair, which later hatched as Nether Drakes transformed by the energy released during the destruction of Draenor. This implies that the lair still exists, however, it is not found in World of Warcraft.
In Beyond the Dark Portal, Deathwing's Lair was never mentioned nor visited, the battle where Deathwing was defeated occurring instead in the Blade's Edge Mountains near Gruul's Lair, and Gruul himself took part in the fight. Not only this, but the reason for attacking Deathwing was not to rescue Kudran Wildhammer, but to retrieve the Skull of Gul'dan which Deathwing had taken. Given this, it is likely Deathwing's Lair has been retconned out of existence, or at the very least any important battle taking place upon it.
Netherwing Ledge (World of WarCraft)
Though probably not intended to be the same landmass (judging by its different position in relation to the main continent of Outland), the floating island south of Shadowmoon Valley known as Netherwing Ledge is likely inspired by the earlier island that housed Deathwing's Lair.