The Dawn War
Little known to the inhabitants of this universe, the Obyriths near completely destroy their own universe. Seeking to cause more damage the placed a Shard of Pure Evil into the boundary between their universe and our own.
Tharzidun found this shard, and took hold of it – before falling made with a desire to unmake reality. However, he retained enough sense to repel its whispers and hurled the Shard into the Elemental Chaos creating the Abyss.
Primordials, Tharzidun and the surviving Obyriths battle for control of the Shard. However, Obox-Ob, an Obyrith claims it, but is destroyed by the Demon Princes; Demogorgon, Orcus and Baphomet. The Shard falls deeper into the Abyss.
Meanwhile, both sides prepare for war, whilst the Primal Spirits set about protecting the world from harm.
Tharzidun, posing as The Elder Elemental Eye marshals the Primordials to try and overwhelm the might of the new Demon Princes. Some join Tharzidun in the Abyss and were corrupted into Demon Princes themselves. Meanwhile the Primordials spread worship of the Elder Elemental Eye, hoping that if he gained the Shard, he could overthrow the Gods.
At this point the Gods, led by He-Who-Was interfered, chaining Tharzidun away in a deep layer of the Abyss, striking his name from the histoy, and renaming him The Chained God. He-Who-Was assigned Asmodeus as his prison keeper.
The war raged for centuries, many Gods and Primordials being destroyed. Eventually the Gods succeeded, after banding together in small groups to destroy or chain them. The Primal Spirits freed the World of Immortal and Elemental Influence.
Then came The Dawn Age.
Wars/Events of Note
Lolth becomes mad after an assault into the Abyss and leads the Drow against their kin, backed by Corellon and The Raven Queen. After the war the Elves leave the Feywild and enter the natural world. The Eladrin continue to reside where they are, splitting into two factions, the Winterkin and the Summerkin.
Becoming spiteful at his position as prison keeper, Asmodeus seeks out the Shard of Pure Evil, claiming a splinter, and crafting it into his rod. He then fights his way back into the Astral Sea and slays He-Who-Was, before removing his name from history – as if the mere mention of his name would be enough to revive him. In his dying breath, He-Who-Was binds Asmodeus to Baator, and in that moment, Asmodeus claims his divinity. He-Who-Was position of guardian of the the Living Gate is passed into the hands of a Mortal.