Alduin couldn't believe it, even as he felt the ebony blade of the dragonborn cut through his scales. He, the world eater, brought low by a cat-man and three ghosts from the past. He had been betrayed at every turn. His father Akatosh had stripped him of his strength as he had entered the world. His second-in command, Paarthurnax, had HELPED the dragonborn learn the cursed dragonrend about that had brought about his destruction with its cursed weight that forced him to land. And one of his own resurrected dragons, that lizard Odahviing, had brought him to the gate of Sovngarde. All of those betrayals had lead to where he was now, on the ground, pinned by the weight of Dragonrend, with the burning sword Dawnbreaker shoved through his ribcage by that damned Dragonborn.
As the dragonborn pulled his sword free, he spoke softly to alduin in the dragon tongue, "Ol lingrah ol Zu'u lahney, hi fent ni naak daar lien."
It roughly translated to, "as long as I live, you shall not eat this world"
Alduin's rage flared at the Khajiit's words and in the common tongue he spoke, "your day will come, Dragonborn, and on that day, it shall be I who carves out your heart with my claws, your blood will quicken my appetite as I consume the world you hold dear!"
With his threat made, he cast his aside his flesh and cast his soul to the realms of oblivion and beyond, intent on finding world on which to build his strength for his return to nirn. Alduin knew he would need a great deal of magical power to regain not only the energy he had expended in his fight with the Dragonborn, but also regain the power that Akatosh had stripped from him. He cast out his senses for a world that would suit his needs.
Near him were two closely knit worlds, one with a dwindling supply of magic, the other a world of seemingly limitless magic. If Alduin had possessed a body, it's face would have had a cruel grin of delight attached across it's face. Alduin's soul passed into the world, it's golden light coming to rest in the middle of a forest.
Immediately, Alduin felt magic rushing into his soul, to much energy in fact, threatening to destroy his soul unless he made a body quickly. Alduin quickly began channeling the magic into a weaving a new body, similar in shape and color to the one he had discarded on Nirn. The familiar shape quickly took shape before him, the blood red eyes, the black scales, the powerful wings, and the razor sharp claws.
Satisfied with his handiwork, Alduin's soul settled into it's new body and immediately felt exhaustion wash over him. The new body was hungry and exhausted, both needs crying for attention. Content that his soul was no longer going to explode, Alduin snapped up a dear and curled up in an abandoned cave to begin recovering. But Alduin didn't know that his arrival had been felt by a select few across earthland and beyond.
A spirit on a hidden island felt it, the waves of malice and power that suddenly appeared out of nowhere. A black wizard felt it in his self imposed exile, the darkness similar to what he possessed. A masked wizard, whose face he never revealed felt it, a magical intrusion into earthland from beyond Edolas. A small guild master felt it, a powerful presence that he knew would affect his children. And a black dragon with blue markings felt it, the arrival of a being whose power rivaled his own, a being who would either be a power ally, or a deadly foe. But Alduin knew none of this. He did not know that his arrival meant he would shape this world's fate as either is unlikely savior, or its ultimate doom. The year was x779.
I'm gonna pause it here. The next chapter all planned out, but is prefer to give you this in chapter instead of assaulting your eyes an big wall of story. Also makes it easier to find your spot. Next chapter will be up either today or tomorrow, where Alduin will learn more of the world he is in. See ya next chapter!