The Celestial War

The Celestial War was a conflict between the Light Gods from the plane of Celestia and the Dark Gods from the plane of the Abyss. It was a brutal conflict that lasted for hundreds of years, nearly wiping out life on Gaia and splitting the central continent into many parts. Seeing no end to the fighting, Dais used his extraordinary powers to seal the Dark Gods off in a new plane of existence, known as the 9 Hells. This came at a cost, however, as the powerful divine magic sealed the Light Gods in the plane of Celestia.

The Conflict
After crossing over from Celestia and slaying the four Elemental Titans, using their essence to create the prime material plane, the Feywild and many of the other planes. Dais and the other light gods began to fill their new world with life, nature and love. However, soon after they had claimed this realm as their own, a group of powerful beings from the Abyss, known as the Dark Gods, crossed over into the prime material plane, instantly beginning to lay waste to its inhabitants. Thanatos, god of law and order, was the first to see them, and they quickly slew him, destroying him and scattering his pieces across the planes for all to see. A brutal war ensued between the powerful beings, with an army of angels and other celestial creatures backing the light gods, while an endless horde of demons from the Abyss backed the Dark Gods. Though Dais stood head and shoulders above all the other combatants, the leader of the Dark Gods, Orcus, was strong enough to oppose him, and thus the war continued for centuries.

Several gods fell during the conflict. During an intense battle over what is now eastern Baelor, Farrah, goddess of fey creatures, and Ravanar, god of shadows and despair, slew one another. Where their bodies fell, the magic of the feywild and the shadowfell bled through to the prime material plane, and the Everglenn and Deadwood were created. Zyra, the goddess of primal instinct and bloodlust, was corned in the Frostland Wastes by Dais's four sons. They felled her, and where her parts fell, dire beasts sprang up, including the Winter Wolf, which lorded of the Fjordland for thousands of years afterwards. Gamorren, the god of destruction, was slain by Helena in one of the fiercest battles of the war. Where they fought, the earth itself broke, forming the broken expanse.

Seeing no end in sight, and watching the destruction that had been wrought on his creations, Dais knew that the only way to end the war would be to force the Dark Gods from the prime material plane. He slayed one of them, a being known as Hellanus, and using his form created a new plane known as the 9 Hells. He then used his divine powers to curse the Dark Gods, banishing them to the 9 Hells forever, each with their own layer to lord over. But every curse has a cost, and so it was that Dais' power forced himself and the other Light Gods from the prime material plane as well, locking them away in Celestia forever, or until Dais breaks the curse.

Aftermath
Though the Dark Gods had been forced out of Gaia, their impact lingered in the form of the Shadowfell, a dark plane that mirrored the prime material plane much like the Feywild. Though the gods were forced from Gaia, others were not and are not barred from travelling between planes, though it takes powerful magic or abilities. The gods can still influence the prime material plane, but only sparingly, and not as directly as they once could.

Gaia eventually healed from the conflict, and those who survived the war slowly began to rebuild and spread. This was the beginning of civilization.