Long ago, there was merely the Continent. The only known sentient race to have lived there were the Gnomes, and shortly thereafter the Dwarves appeared, around five thousand years ago (roughly four thousand years before humans). They two races met peacefully, as they had a similar way about them and the Dwarves were not looking to expand and conquer. Two thousand years later, the Elves arrived on their white ships from another world. The Elves expanded and grew powerful, and though they weren't war mongering, they were less peaceful and fought various wars against the Dwarves, as well as lesser known races such as the reptilian Vran and the hairy Werebbubbs.
And then, an event known as the Conjunction of the Spheres occurred. A cataclysmic event where various rifts opened between worlds and creatures from other planets and dimensions were transported back and forth between planes. Many, in fact
most of the monsters the Witchers hunt appeared during this time (such as Dragons and Vampires), as did humans, who were transported from their homeworld (Earth) that they themselves destroyed. The humans, able to breed far quicker than the Elder races, spread across the Continent, and after a succession of wars against the Elves, became the dominant species this side of the Blue Mountains.
Those Elves that survived became servants, or went into hiding. The Gnomes, introverted as they were, live with the Dwarves or in small communities in the mountains. Lesser known peoples like the Halflings, Vran, and Werebbubbs became nearly extinct, but some of them still live in the current era in small pockets. The Dwarves came out the best (though still second class citizens), integrating into human society easier than the others as they are skilled smiths and bankers.
In the 10th century, a group of Sorcerers and Kings came together and discussed the geopolitical climate of the Continent. The Elder races themselves had been mostly handled, but there were still various beings that had not yet been exterminated, imprisoned in camps, or integrated into human society. These were the monsters. And so, the Witchers were made. Originally meant to be Magic Knights to quell the last bit of resistance this world had left against the humans, little did they know that the monsters would not be exterminated so easily, nor would the Elder races fade peacefully. They also did not realize how grueling and torturous the trials to become a Witcher were, nor what that would do to someone's body, but they also cared little as long as they got the job done.
It has been one thousand, two hundred and sixty five years since the Conjunction of Spheres, and two years since the Battle of Sodden Hill that halted Nilfgaard's advance. Now it is up to you, to help push back Nilfgaard, before they attack once more...
Factions
The Northern Kingdoms: A loose collection of germanic-esque kingdoms that warr with one another for power, though they share a common culture and ban together when faced with a larger threat. There is a huge list of Kingdoms, but even big fans of the series sometimes cannot tell them apart as the political landscape changes book by book and game by game.
Nilfgaard: An Empire that was once seen as a backwater laughingstock at the edge of the world, in recent years it's been rightfully feared and has attacked the North, conquering a few of the southern Kingdoms. Rumor has it they are once again preparing for invasion. They worship the Sun.
Witchers: Essentially Super Soldiers with no political affiliation. They are taken as children and mutated through both science and magic to gain superhuman strength, toughness, fortitude, senses, and speed. Though some Witcher hire themselves out exclusively to certain clients like a King, they are beholden first and foremost to their school. There are the Schools of the Wolf, the Viper, the Bear, the Cat, the Manticore, and the Crane.
Scoia'tael: Non-human guerillas also known as the Squirrels, due to the squirrel tails they wear on themselves. They're terrorists to human Kingdoms and freedom fighters to non-humans. Recently employed by Nilfgaard with promises to grant them a Kingdom of their own, they're deadly ruthless in their hatred for humanity.
Blue Stripes: Temeria's Special Forces and Secret Police, lead by Vernon Roche.
People of Interest
King of Temeria. Has humped his sister and half the women in his Kingdom. Isn't well liked by other nobility and some of his people, but his soldiers adore him and he's known for his military genius and forth-right nature.
Oldest son and bastard of Foltest and (apparent) leader of the expedition, he claims he seeks to gain his inheritance by fulfilling his father's wishes here. He's known as an avid fighter, an experienced sailor, and he is a supporter of nonhuman rights.
A beautiful and talented Sorceress and Advisor to Foltest, Triss is a skilled healer and battle mage and former lover of Geralt of Rivia. She is called "Fourteenth on the Hill" after the Battle of Sodden Hill, as she was believed to have been one of the thirteen to have died there when she had in fact survived.
The ruthless head of the Blue Stripes, Temeria's Special Forces. Vernon Roche is an ardent patriot and loyal to a fault, following his King's orders without hesitation. He's not one to cross, particularly with talk of treason.
Former Hedge Knight and current Emperor of Nilfgaard. He is an intelligent ruler, a brilliant statesman, but expantionist and power hungry to a fault. He brooks no wound to his pride, and seeks to dominate the North. In contrast to the Northern Kings, nonhumans generally seem to support him.