Nihilam

Nihilam, the Doom World, is a planet in the Great Dark Beyond where Sargeras and his Burning Legion killed the members of the titan Pantheon at the start of the Burning Crusade.

History
After Sargeras began his Burning Crusade to scour the cosmos of all life, the Pantheon confronted him near Nihilam. The titan Aggramar, former friend and student of Sargeras, approached the fallen champion, unarmed, thinking that he could still be reasoned with. But Sargeras was already set in his ways, and nothing the Pantheon said could ever change his mind, and so, with a howl of rage and sorrow, Sargeras struck Aggramar with his ruined blade, the sword nearly cleaving the titan in two. Outraged, the Pantheon launched an all-out assault on Sargeras and his Legion. Stars withered and died as the battle raged across the cosmos, and Nihilam, known thereafter as the "Doom World", became twisted and scarred by the apocalyptic conflict.

The battle only came to a close once Sargeras had ended the lives of every member of the Pantheon with a gigantic storm of fel magic. Sargeras declared his Burning Legion victorious and set off to find the powerful world-soul Azeroth, unaware that the titan Norgannon had managed to launch the spirits of the Pantheon out through the Great Dark to temporarily escape the destruction of their bodies.

The war between the Pantheon and the Legion shook the fabric of creation around the Doom World and infused its metal ores with otherworldly properties. The metals became nearly indestructible, and when viewed in just the right light, the materials reflected brief images of the battle between Sargeras and the Pantheon. Most important of all, the metals also leeched away the essence of any living thing that touched them. The eredar smith Netrezaar used these metals to create his life's work, the massive axe known as the Maw of the Damned.

During the War of the Ancients, demons poured out of a portal from Nihilam to Azeroth opened by Balaadur at Black Rook Hold, implying that the planet is now under Legion control.