Homo Immortalis are the biological apotheosis of human evolution. They possess incredible physical and supernatural power, easily on par or mightier than the New Gods dwelling on Earth. They were engineered by the Celestials from ancestors of Homo Sapien stock approximately 50,000 BCE. There are two primary tribes of Eternals-- the Forever People of New Genesis, and the Titanians who relocated from their original home on Earth to settle the outer planets of our solar system.
Homo Immortalis are vastly stronger than most humans. They possess physical capabilities equal to the other godlings; most of them can lift 20 or more tons and endure extremes of impact and temperature. All Homo Immortalis can fly by telekinetically manipulating the gravimetric fields around them to achieve sub-sonic flight. They are also capable of varying levels of telepathic contact, though few of their number can do more than send and receive simple messages with others. Their connection to the Power Cosmic provides a tremendous (but risky) reservoir of energy to bolster their abilities. However they do not share in the fruits of the Demiurge's power; they cannot mystically summon boomtubes to traverse Yggdrasil. They lack the AllSpeak and have no innate connection to magic. Despite their vast powers, and being engineered rather than created by magic, Homo Immortalis share one common trait: they are mortal. Long-lived, but not truly immortal, and each of them has a soul with a harmony that transcends the demesne of their birth.
Those Homo Immortalis who fought against the Celestial invasion during Ragnarok stumbled upon a radical concept: the Uni-Mind. It was a deliberate merging of thought and effort, of personalities and intention, all powered by the limitless potential of the soul itself. This gestalt entity contained all the power and will of the entire race of Homo Immortalis who opposed the Celestials. With it they were able to channel the collective might of all humanity, of all the races of the Demiurge, and scour away the Celestial 'infection' threatening the Demiurge. Never before, and never since, has it been used; some question if the Demiurge, or Homo Immortalis, can even weather such an event again without it destroying them utterly.
Celestials engineered Homo Immortalis shortly after the failure of the Kryptonian experiment. Despite Oa's meddling, the Kryptonians were the best success they had achieved in billions of years. Covertly they visited the Demiurge to see for themselves the origin of the incredible powers that had checked that vast military force. Upon discovering the Demiurge, Celestials engineered an artificial demesne and seeded it with their genetically perfect human specimens. With the world of New Genesis as a control, the Celestials created a second colony on Earth. In both realms, Divergents-- genetic experiments-- were allowed to roam free as part of a long-term wildcard project.
Earthbound Eternals dwelt on Earth in the city of Titanos, and became known as Titanians. Some followed the Celestial edicts to continue their scientific research and others pursued their own interests. Strict breeding programs suppressed reproduction rates. A control group was created in an artificially-engineered demesne called New Genesis, and they called themselves the Forever People.
A 'lesser' form of Eternal, called Homo Descendus, were developed as wildcard experiments. These 'Deviants' were not part of the control group and were allowed to roam freely. With a high percentage of superhuman traits the Deviants successfully established a highly advanced culture on Earth well before the rise of any human civilization. They occupied Lemuria and resided in the eco-sphere of the Savage Land.
After the events of Ragnarok, Oa launched a sterilization campaign much akin to the one they'd afflicted the Kryptonians with. Divergents died off in massive numbers until barely a scarce handful remained. Darkseid and Thanos are both Divergents, and survived the pogrom thanks to their incredible personal power.