Originally the same species as the Alterans, the group that would later be called the Oans left the Alteran home galaxy and traveled to the Centera Galaxy, located near the center of the universe. To separate themselves from Alterans, they took the name Oans, which when translated from Alteran literally means “Guardian” and named their homeworld Oa (meaning “To Guard”). They remained in communication with Alterans and the Whills for awhile, but over time communication became less and less frequent to point where the Oans disassembled theirs and any of the nearby Stargates for the raw materials.
The Oans believed that the Force should be used to observe and understand the universe itself. As their understanding of the Force grew, it allowed them to become semi-immortal beings of incredible power, similar to that of the ascended Alterans, but without having to leave their corporeal form. As the Oans evolved over time on the planet Oa, their physical appearances changed to greater differentiate themselves from their Alteran ancestors. Currently, the Oans resemble short blue-skinned humanoids with white hair.
As they observed more and more of the universe, their mission became clear to them: Create an orderly universe and protect it from all of the evil that is out there. Using the raw materials from the deconstructed Stargates, the Oans created a Central Battery that allowed them to collect and store massive amounts of Force Energy. By accessing and manipulating the collected energy, the Oans were able become even more powerful and allowed them to pursue their goal of a more orderly universe.
To ensure that their mission would become a success and to guard against evil menaces across the universe, the Oans originally created a legion of robotic sentinels called the Manhunters. However, the Manhunters eventually became sentient enough to resent their servitude and were viewed by the Oans as flawed due to their inability to reason. For the Manhunters, things were either good or evil, with no room in-between. The Manhunters eventually rebelled against the Oans. They left into unknown regions of space where they formed their own robotic society where they were able to pursue their own agenda (which often included trying to destroy the Oans).
To atone for the failure of the Manhunter program, the Oans decided to use living beings, who had free will and strong moral character to protect the universe. To arm their new legion of galactic protectors, the Oans created power rings that allowed the bearer to access a small portion of the Force Energy that was stored in the Central Battery. The power rings allowed the wearers to project green beams of energy with which the bearer could conjure objects of any size or shape, the only limitation was the wearers’ imagination and willpower. These protectors became known as the Green Lantern Corps.
The Oan created the Green Lantern Corps some three billion years ago and the force has survived multiple rebellions, murders, and collapses from within and without.