Averniad

The Averniad was the mythical war between the forces of Mount Celestia and Elysium over control of Avernus, which at that time was a paradise.
The full details of the conflict are unknown to mortals, for it is said that a mortal lifetime is not long enoguh to hear the full complexity of the tale. However, much of the story of the Averniad is dominated by the Great Betrayal, when Ashmedai, Celestial Marshall and commander of the Legions of Heaven, wrenched control of Avernus away from both Mt. Celestia and Elysium, claiming it for himself and dragging it into the Eight Hells to serve as Hell's ninth plane.
Ashmedai's betrayal was accompanied by scores of his legions, who followed their marshall without question. Many angels resisted Ashmedai's commands and attempted to fight or flee. Among those that turned against their marshal was the young angel Zariel, who led a small band of angels to escape Avernus as it was hurtled through time and space to Hell. However, few of Zariel's companions survived the journey to freedom.
Following Avernus' arrival in Hell, Ashmedai become Asmodeus, and his legion of fallen angels conquered Hell, proclaiming him its new ruler.
Though a story known in many of the Outer Planes, the tale of the Averniad, complex and ancient as it is, is one of many stories told about the origins of Asmodeus, and there is no consensus on its veracity.

Conflict Type

War

Conflict Result

Celestial Marshal Ashmedai emerges victorious after betraying the Seven Heavens; Avernus becomes the ninth layer of Hell