This fic is concept of a hypothetical story that could have happened if Westeros replaced Seanchan, with both histories as intact as possible, until the main stories start. All concepts are split over 16 hypothetical books that cover the story. What would have happened if George R. R. Martin and Robert Jordan planned one story on two different continents, eventually combining it into a single narrative? I will try to answer that question.
Every book (or a few books together) will get summaries of their events. The less changes are present in the story, more books will be summarized alone.
First, we will start simple: combined mythology, history and background of both worlds.
The Wheel of Time turns and ages come and pass, leaving memories that become legend, legend fades to myth and even myth is long forgotten, when the age that gave it birth comes again.
The nature and cosmology is complex. The Creator created the Wheel and let it move, in endless cycles of rebirth. His counterpart, the Dark One, named Shai'tan, the personification of evil, was imprisoned outside of the Wheel. And the One Power that moves the Wheel is split into two halves: saidin of men and saidar of women. There are other sources of power and magic too, but the One Power is the supreme force in the universe.
In an age of the Wheel, called the Second Age by some, an age long gone and an age yet to come, humanity reached the zenith of civilization, with male and female channelers leading it. But this didn't last long. Some channelers accidentally discovered the prison of the Dark One, creating a bore in it, allowing him to touch the world. A great war started, the War between forces of light and those loyal to Shai'tan. Some channelers joined Shai'tan, the most powerful of them becoming the Forsaken. And one of these Forsaken was Aginor, a great scientist and investigator.
Using a mix of twisted science and Dark One's dark sorcery, Aginor created many horrible creatures, breeding humans with animals and monsters, but also using other techniques. He made Trollocs, Myddraal, Darkhounds, Draghkar and many other horrible creatures. But it wasn't enough. He got frustrated, seeking to create perfect weapons and monsters, the Dark One himself wanting the same.
So Aginor went to the far land in the West, followed by Shai'tan himself, and deceived the young race, later called the Children of the Forest, whose lands were getting invaded by humans. Aginor and Children of the Forest captured many humans and created those perfect weapons: cold, ethereal creatures, powerful bringers of cold and winter, beautiful and inhuman, bringing cold and death wherever they go. What was so special about them was that they could raise the dead as wights, turning every loss of either the Shadow or the Light into new soldiers. They were immune to most weaves of One Power, except the most powerful ones, like balefire and deathgates. The only weapon that could defeat them was obsidian.
Later, Aginor also created creatures of fire, reptilian beasts who could fly and breath fire, who were later called dragons. Aginor created these creatures inspired by the banner and title of Lews Therin, the Champion of the Light.
Eventually, Lews Therin defeated the Dark One, but not without consequences. Dark One touched saidin and all male channelers went insane, causing a cataclysm around the globe. Lews Therin himself slaughtered almost his entire family. And Valyrian and Westerosi legends took many inspirations from this, like the tale of Azor Ahai killing Nissa Nissa. But not all of Lews Therin's children and kin were slaughtered - some kin survived, and so did two children: these two children would become important in history of the world.
After the Breaking of the World, the Others were driven to the land of Westeros, and defeated by the Last Hero, a descendant of Lews Therin. The Wall was built, using the power of the Children of the Forest and few channelers that remained there and the strength of giants and men. However, a few thousand years later, Luthair Paendrag Mondwin, son of High King Artur Hawkwing, went to Westeros with his ships and his people, called Andals by Westerosi. The Andals conquered all of Westeros, save for the North, which resisted.
Meanwhile, on the huge island of Valyria, east of Westeros, other descendants of Lews Therin discovered ancient experiments of Aginor: dragons. They mastered these beasts using a specific, but otherwise weak, type of channeling, and in order to keep it in their bloodline, they adopted incest. And soon they built a powerful empire, rivalling the one of Artur Hawkwing. But no empire lasts forever. And in a cataclysmic event, known only as the Doom, Valyria was ruined, and it's knowledge lost and all of dragons died, except those of one family: Targaryens.
Hundred years later, Aegon Targaryen, with his sister-wives Rhaenys and Visenya and their three dragons, conquered Westeros, forging the Iron Throne and proclaiming himself King of the Andals, Rhoynar and the First Men, Lord of the Seven Kingdoms and Protector of the Realm. And Targaryens still rule, through their branch family of Baratheons, while the main line ended with Aerys II, whom they called the Mad King. But the dragons were lost long ago, when they all died in a Targaryen civil war named Dance of the Dragons.
Today, Westeros and the lands on the East, that Westerosi still like to call the land of Artur Hawkwing, do not maintan great relations, and also two continents operate quite differently when it comes to politics and state government, with Westeros still being a feudal system. There is some trade and contact, and there have been some conflicts, though it was mainly the case of the Ironborn raiding and pillaging as usual. But nothing of any high significance happened for a long time, primarily because of Westerosi hatred for the "witches of Tar Valon" and all kind of magic. So Westeros and Land of Artur Hawkwing stayed out of touch for a long time.
That is, until the Hour come...