The eternal war between two Realms for control over Aequus
"Have I told you the story of how our world has come to be, my child? It was a long time ago, when an eternal war raged between two worlds..."
History and legends say that before the Calamity humanity had no Magic, but they thrived with technological advancement. Despite that, unknown to them, two Realms have been fighting a neverending war in the background to settle who would have control over Aequus, the Realm where humanity resided, our universe. These Realms, Caeles (often called "Heaven") and Mors (often called "Hell"), complete opposites to one another, have been warring for eons, under the belief that the Humans were their key to gain more knowledge about their Gods, the Dragons.
The beginningBoth Caeles and Mors were created by Tiamat, the Mother of All Things, each representing a half of the basic concepts that make up existence, also known as the Elements of Magic. This put Caeles, the Realm of Order, and Mors, the Realm of Chaos, in natural rivalry and, as soon as they found a way to open the Realm Gates, they started fighting over their differences. Back then their conflicts were small and didn't result in big losses for either side - until Aequus and humanity entered the game.
The Realm of BalanceReaching near the peak of their technomagical advancement, the people of Caeles realized that in order to achieve their objective of ascending and meeting their creators, they had, first, to meet Balance. To them, they were unable to reach that status, as they were naturally only half of Tiamat's creation. And to that end, a short-lived truce was made with Mors, so they could create a new world, a Realm of Balance: Aequus. Magic of such scale left both sides greatly weakened, as the Aether they used had to fuel Aequus's birth and keep its fabric woven tight.
Not long after, standing before raging balls of fire forming the new universe, they assumed the experiment was a failure and war broke out once again. What they did not expect, though, was that from a small planet life would spring eons later, proving the creation was actually a success. They warred over the rule of the planet, sometimes bringing their battles to it and laying destruction over its lands and creatures. But the war seemed pointless as after so long there was no sign that anything, not the planet itself nor its instinct-driven creatures, would in fact take them to the Dragons. With their war cooling off once again, what they didn't expect happened: a single species would misteriously receive the blessing of balance. The humans, still in their infancy as a species of civilization, were intelligent and had the ability to weave all elements. This sparked new hope in both Caeles and Mors, which would battle evermore ferociously to take a chance at controlling Aequus.
The Dragons' ChosenThe sister Realms' war broke into Aequus many times again. But now, something was off: there was a third side in this war. Every single time Caeles, Mors, or both came to Aequus, 9 individuals among humanity would receive great powers and rise to push the invaders back and away, able to achieve feats of magic either Realm could not stand agaisnt. But that was not all. With every battle ended, these warriors, or at least those of them who survided until the end, would lock both Realms away from Aequus and somehow history would be rewritten in both evidences and memories, as if time itself had rewinded and the battles between Caeles and Mors never took place for humanity.
Time and again did they try, only to be expelled from Aequus every time. This was a whole new challenge to them, one them both threw all they had into surpassing, never forgetting their enmity, but it was for sure a sign of the Dragons' intervention. Conquering humanity would mean reaching their gods, that was for sure. With an eternal war behind them, losing to The Nine was no reason for either Realm to give up, but a motivation to try harder through different approaches.
The CalamityHumanity suffered dozens of attacks from both Caeles and Mors, but every time one or more of the Nine were either killed in battle or never found, resulting in a weaker seal that would only keep them at bay for so long. But in the year of 2062 AD, thanks to the clever prior measures and guidance of a renegade from Mors, the Nine were united and trained and successfully fended off the attack that came from both Realms.
With this, the world would change forever. The sealing of the Realm Gates was now made permanent by draining most, if not all, the aether from both Caeles and Mors and bringing it to Aequus, preventing them from opening new gates. This ended the war, but also reshaped human civilization. So much aether, enough that fuelled two worlds, made magic much easier for the common people to weave, but made useless most of the technologies available. Besides that, the "time-reset" that always happened after the Realm wars didn't come, and humanity would have to rebuild by themselves.
This marked the beginning of a new age for humanity: The Aetherial Era.