The Sundered Realm
That was when the Watcher in the Dark decided to act.
Leading the Endless Horde made up of Giants, Dragonborn, Shifters, Elementals, Drow, and Dragons, along with gnolls, goblinoids and orcs through a portal to the shadowfell, he was able to move the lost empire of Netheril back onto the material plane, strengthening his numbers with countless shades and shadow creatures. It was the greatest army ever assembled.
When the alliance realised their depleted army could not stop the Horde, they resorted to drastic measures. Creation forges, banned because they steal life from the earth to give birth to the Warforged, were restarted. The Hand of Death, a band of human necromancers, were promoted to generals and given the task of creating an army that would rise no matter how often it was defeated.
The two armies met on the endless Fields of Thandor where the war raged for a decade without a clear victor. Desperate and scared, the God Kings came up with a secret and dangerous plan: to steal to power of the Elder Gods.
Armed with the Godsbane, a sword forged at the Dawn of Time, Cyric travelled to the Realm of the Elder Gods in the Astral Sea while his twin Sister Midnight sought out the Gods’ Avatars on the Material Plane.
Cyric, a demigod himself, stole the tablets of fate while Midnight battled the avatars, giving her life to distract them.
Returning to the Material Plane, Cyric rode into battle with the Tablets of Fate and claimed all the gods portfolios for himself. Momentarily he became the most powerful creature in the world, channelling the powers of all the gods at once. However neither Cyric nor the material plane could contain that power. The Horde and the Alliance were both defeated, Cyric dissolved into nothingness and the whole Material Plane started to follow, breaking apart piece by piece.
The Humans, used to order and civilization, soon fell to the remnants of the Horde who thrived in the chaotic Sundered World. The Hand of Death claimed its own realm, the Warforged proclaimed their freedom.