'Why, by Gwyn's Lightning, did I think this was a good idea?' thought Ignis to himself as he burned... and burned... and burned all the more. One wonders what brilliant idea Ignis had, to have an end result of a nigh eternal immolation. It is a truly remarkable, selfless idea; an idea not at all influenced by his increasing fatigue at repeated the Gods damned cycle of fire, blood, ash, and death. Recognizing that he was losing himself, and that no one else would, could, or should be expected to step up to the altar as the next sacrifice, he decided to do something drastic. Something that would alter what was made law at the beginning of time itself. Something decreed by the gods who bore the strength of Lords within their souls, by the Gods that overthrew the reign of terror that was the Age of Ancients, slaughtering all (but two) of the Everlasting Dragons in order to usher in the Age of Fire.
Ignis, recognizing his own inability to continue being the backbone of an inherently flawed world, took it upon himself to fix the world before he invariably was broken by it. In order to do this, he would have to take Humanity, a race literally born from the dark, and strip them of the dark, replacing it with whatever he could. In hindsight, it was both brilliant and stupid beyond measure.
Brilliant, for it would allow him to let the flames finally flicker and die without fear of man losing itself to its dark, as Manus and the entirety of Oolacile did.
Stupid, because the Dark is a living, violent parasite that would never willingly be separated from humanity.
Stupid beyond measure, because the Dark, once separated from the species it had for so long been a part of, would do everything within its power to kill those that forsook it, whether or not they know of its forsaking.
However, this all pales in comparison to the truest problem he faces in the thrice damned Kiln. His truest plight is that, unlike before, he must remain lucid, conscious of how the world shifts as he rips it apart in order to rebuild it in a better condition. Before, he would simply burn for a few seconds before he felt the fires pulse out, allowing him to sleep, and reawaken in the Asylum, reminiscent of his first awakening there. Now, he must remain strong enough to guide a living, uncontrollable power; a power that could quite easily destroy all he is trying to accomplish. Now, he must guide the flames as they refine the world, and humanity with it, in the most painful of ways. Now, he must remain awake, lucid, and focused, for what could take minutes or centuries.
After what seems -and could very well have been- an eternity, his job is finished. The First Flame has refined the world, refined humanity. The world is now as whole as he can make it, and humanity is suffused with the powers of the Lord Souls. While their strength will not match that of the gods for a great while yet, if ever, they will be more than capable of defending themselves from the remnants of the ages past.
And with his job done, with humans finally able to live in the dark without fear of succumbing to it, he allows the pain of millennia spent immolating to come crashing down on him. Utterly spent, delirious with pain, and half blind by the gods damned ash in his empty eye sockets (he never understood how he retained his sight), he barely manages to think, 'That glow looks rather like a soul,' before he collapses into the ash, right into the warm, flame-like glow so reminiscent of a soul. As he slowly realizes that the orange glow looks like a soul because it is a soul, it is already well on its way to being absorbed by him.
His final waking moments are spent directing the energy of the soul to heal him. Upon doing this, he releases his desperately tenuous grip on the waking world. For the first time in possibly thousands of years, he sleeps.
Time passes as the hero who saved man from a fate worse than any death slumbers within the kiln. Nations rise, and as man expands, a golden era begins. Sciences are taken far beyond what they were believed to be limited to, as arts of the soul and mind take to new depths and heights. During this time, the first grimm is spotted. Treated as an amusing nuisance, it is ignored.
As grimm sightings become more common, people think less of the threat of the grimm. As time goes on, ever forward, the grimm prepare. They wait. They scout. They LEARN. And at the apex of the golden era, they strike. Used to a peace earned by the actions of those long passed, they are utterly unprepared for the grimm, and they pay dearly for it. Each dusk brings another hellish night of fighting; each dawn brings news of the dead; each day brings humanity closer to the death they so narrowly avoided so long ago. As time passes, they relearn to fight, using strength of arms forged from the plows of the fields and strength of souls forged from the desire to live. It is through this struggle they learn more of the grimm they so readily ignored before.
They learn that whatever god designed the grimm did not deign to give them souls. The grimm, beings of pure dark, had no need of food, water, air, or sleep. The grimm were not alive, and were not capable of withstanding the power of a soul. And the very world they reside had a soul, one channeled through the very bones and blood of the earth. Once mankind discovered this, the fight turned. While they would never win (for who can kill that which was never alive to begin with?), the soul crystals they discovered very quickly became a fundamental part of the defense of the few remaining bastions of man.
When the grimm realized that they were losing far more than they were gaining, they left. No more were they bathing in the blood of hundreds. No more were they slaughtering the weak as the defenders remained hard pressed to fight the teeming horde. Now, they were fighting on lesser footing, as even the weakest of their prey could slay dozens with a single spell, so long as they had sufficient crystals. And with this knowledge, they retreat, hoping that their prey's advantage quickly runs dry.
As time passes, the last bastions expand fully into kingdoms. Mankind, while few in number, were resourceful, and they expanded; growing in strength and number, they slowly expanded. Two hundred thousand years have passed since Ignis finished his immolation. Now, he must awaken, and awaken he will, within a world he scarcely recognizes.