OMG UBERGAMING WTF
The fallen souls of the great heroes and villains who each played a key role in the conflict between the Abstracts and the remainder of Creation refused to surrender themselves to Death’s embrace. Instead, they chose to remain outside of the purview of any deity’s dominion, for they had not only fought on gods’ behalf, but in many cases, simply for their own self-interests or for the sakes of those mortals whom they held in high regard.
Furthermore, the gods found themselves at odds: if those few souls who had actually fought with the backing of a god allowed themselves to be claimed by their patrons, a strange, uncertain balance of power would occur, and now, more than ever, solidarity amongst the factions of divinity was crucial.
Therefore, a dwelling place of sorts was created. Through the centuries and millennia, the kept souls (called Eternals, for they would remain until the End of Time,) grew restless, until one of them simply left.
Drifting along the strands of the Time Stream until it made contact with a mortal, the soul known as The Champion (the original names of the Eternals have been lost to time, as far as mortal reckoning goes) lent its wisdom and courage to a mortal whose own soul resonated with its own, and aided this mortal in preserving the balance of Law and Chaos in his world, until the Caretaker retrieved the wayward spirit.
Upon some reflection, the Caretaker began to see the potential benefits of allowing the Eternal Souls this leeway. Balance among the aspects of Creation could be further preserved, for mortals of all shades benefited by the actions of the Eternals, and the restless souls were allowed a measure of release from their captivity. The Eternals have never been allowed to possess or replace their chosen (The Champion would never have done this, but this rule was set in place because the Caretaker feared what might happen if any of the Eternal souls were allowed to reincarnate fully. For if they were to die, Death might lay claim to one of them, and they would be lost forever, in addition to them falling under Her sway), instead touching mortals in the way the beings known as vestiges might, experiencing the sensation of the living world in exchange for guidance or in some cases, power.
Each creature touched by one of the Eternals shares a soul-deep resonance with all the others that have come before it and will come after it. Because the Eternal souls do not actually reincarnate in the bodies of the creatures they choose as their vessels, the nature of an individual Eternal souls’ influence is not limited to a single creature at a single time- there might be three Eternal Champions in the multiverse at once, for example, but never on the same world. Additionally, because of the nature of this bond, a creature’s connection to the Eternal soul that is guiding or aiding it may wax and wane over time.