The Oans are technologically substantially advanced, cunning manipulators and far-seeing strategists. Oa has no culture except what their armies bring back to them. Oans are cold and merciless, almost universally obsessed with preserving law and order.
Oa is one of the oldest races in the universe. Locked in an endless and eternal war with the Celestials, Oa has been an instigator of many proxy wars and cultural shifts across the galaxy for the last billion years.
The modern Oans derive from an even more ancient race called Maltusians, one of the first organic races to arise in the now-destroyed First Firmament. They were born with an inherent capability for controlling the Emotional Electromagnetic Spectrum, a source of energy derived from the willpower of all sentient beings.
The Maltusians were lifted out of their rather primitive lifestyle by The Watchers early in their civilization's development. This proved to be a catastrophic choice, as the Oans rapidly developed into a Class IV civilization and engaged in violent encounters with the Celestials.
The first major play of their endless detente came when they armed a faction of Celestials called the Aspirants with the Godkiller; weapons to combat other Celestials. The Oans assisted the Aspirants in deploying the weapon at the heart of the Source itself in an attempt to prevent the Celestials from accessing the Power Cosmic.
The deployment of the Godkiller weapons cause immense, incalculable harm to reality, breaking it into billions of multiverses segregated by P-brane frequency. The mightiest minds in the universe even prognosticate that the multiverses might never collapse into itself again, resulting in a multiverse that will eventually wither and flicker out of existence.
This resulted in the Watchers withdrawing from the universe and protecting their own technology jealously. In order to maintain their detente with the Celestials, the Oans continued to arm and educate other races to ward off the immense might of these ancient powers.
Oans had begun to analyze and even control magic, in the earliest days of their ascendancy. One of their earliest battles was against the forces of entropic necromancy, battling the Empire of Tears, an early offshoot of Celestial engineering. They successfully destroyed the weft of magic in dozens of sectors-- condensing all that power into a meteor that would become the Starheart. This early experiment prompted them to attempt to coalesce magical power into a more permanent and stable power structure.
Over time the Oans consolidated their collective cosmic power into the Green Central Power Battery on Oa, creating a repository of surplus energy that could supplement their already awesome powers. They poured their technology into creating a surplus of Willpower that could exceed what any single Oan could accomplish on their own.
Oa focused on refining their mastery of the Electromagnetic Emotional Spectrum. This innate power and advanced technology made Oa proof of Clark's Dictum that any sufficiently advanced technology is indistinguishable from magic. In the case of Oa, there was no longer a divide between magic and technology. This allowed them to create the legendary Green Lantern Rings, some of the most powerful artifacts in the universe.
The Krypton Detente
The most significant event of the last fifty millennia was the rise of planet Krypton and the Kryptonian Hegemony. The military might of Oa was strained to the breaking point trying to contain them, depleting the entire reserve of their Manhunters. Oa enlisted allies such as the Kree in the battle, and helped the mad god Darkseid tap into the power of the Omega Force. When their Manhunter robots were destroyed, Oa constructed new virtual intelligences inside crystalline rings that were directly connected to the Central Power Battery. These rings were given to sentients who possessed extraordinary willpower and focus, making them formidable foes for the Kryptonians.
Oa attempted multiple other strategies, but their most far-reaching one was the creation of the Demiurge. A sentient magical presence, the Demiurge was guided into producing armies to fight Krypton. The most prominent of these New Gods was Buri of Asgard, who led the armies of Asgard to crushing victories over Krypton.
The military rout was launched along with genetic plagues, radioactive bombardment, and even dimming Krypton's main sequence star. Sabotaged from within and without, Krypton passed into history when the last of the Kryptonians saw their sun go nova as the Oans implemented their final sanction.