The "Witcher" series is based on a number of fantasy books written by Polish writer Andrzej Sapkowski. Set in a medieval fantasy world, the games center on the witchers - a secretive order of warrior-monks that hunt supernatural creatures. Witchers train their entire lives and possess superhuman abilities through the use of mutagens and alchemy.
In the games, players take control of Geralt of Rivia, a famed witcher. As the games progress, Geralt regains his lost memory, and is embroiled in a number of conflicts and disputes between kings, kingdoms, and even different races, all while being pursued by the ghosts of his past - the otherworldly Wild Hunt.
The Wild Hunt
The Wild Hunt is a group of spectral riders that appear periodically to terrorize human populations and take special individuals hostage. The Hunt is central to Geralt's story, as they are suspected to have kidnapped him and his lover, Yennefer, in the past, and are responsible for his amnesia.
The King of the Hunt stalks Geralt throughout the first game, making cryptic references to his past life. The Wild Hunt returns in Witcher 3 as the primary antagonist, seeking to capture Ciri, Geralt's adopted daugther and witcher-in-training.
The Northern Kingdoms
The Northern Kingdoms is a term used for the group of states ruled by kings in the north of continent, including Temeria, Aedirn, Cintra, Kaedwen, Redania, and other minor kingdoms. Individual kingdoms often war against each other; only the threat of invasion by the Nilfgaardian Empire from the south is enough to make them unite together.
'The Witcher' takes place in Temeria and Kaedwen, 'The Witcher 2' in Temeria & Aedirn, and 'The Witcher 3' will reportedly take place in multiple areas.
The Nilfgaardian Empire is a large, powerful state located immediately to the south of the Northern Kingdoms. In many ways similar to the Roman Empire, the Nilfgaardians seek to use their massive, experienced army to conquer the known world, and to spread their supposedly superior culture and civilization.
Conquered lands are turned into "provinces", usually ruled by locals as long as they submit themselves to the Emperor. The Empire plays a big role in Witcher 3, with trailers showing Geralt meeting the Nilfgaard Emperor, Emhyr var Emreis.
The Scoia'tael, known in human tongue as the "Squirrels", are a group of non-human rebels - elves, dwarves and halflings - that are fed up with human racism and discrimination. They have chosen to take up arms against human oppression and dominion. The Scoia'tael are a key organization in the Witcher series, providing Geralt with the choice of allying himself with either the human or the non-human side.
Most of the Scoia'tael are elves. Prominent members include Yaevinn (Witcher 1) and Iorveth (Witcher 2). The Scoia'tael do not play a central role in Witcher 3, but are involved in several side-quests.
The first game begins with Geralt being found by his companions, near death and with total amnesia. He recovers his strength at Kaer Morhan - an ancient witcher fortress and school. Shortly after, Kaer Morhan is attacked by a mysterious criminal organization known as the Salamandra. They manage to steal ancient witcher mutagens, which give the Witchers their superhuman abilities. Geralt follows the trail of the Salamandra to Vizima, the capital of the kingdom of Temeria. Here, he is embroiled in a conflict between humans and non-humans (elves, dwaves, and halflings), and can choose to take a side or remain neutral. Geralt continues his investigation to find the leaders of Salamandra.
As the city of Vizima is torn by civil war, king Foltest finally enters the picture, and contracts Geralt to find and kill the head of Salamandra - the Grandmaster - to restore the peace. Geralt discovers that the Grandmaster aims to use the mutagens to transform the entire human race, in order to survive a supposed end-of-the-world scenario. Geralt defeats the Grandmaster and is rewarded by the King. The game ends with Geralt saving Foltest from an assassination by another witcher.
The Witcher 2: Assassin of Kings
The story continues on immediately from the first game. King Foltest has hired Geralt as his bodyguard, following the attempt on his life at the end of the first game. Geralt aids Foltest in capturing the castle of a rebellious baron. Shortly after, Foltest is successfully assassinated, and Geralt is blamed for his death. The commander of Foltest's forces, Vernon Roche, helps Geralt escape prison and death, believing him to be innocent. With the aid of Roche and Triss Merigold, Geralt sets out to track the king's killer.
Arriving in the trade city of Flotsam, Geralt is embroiled in new conflicts between Scoia'tael rebels and humans, and other subplots. It is revealed that the assassin is also responsible for the death of Demavend, the King of Aedirn. The assassin kidnaps Triss and Geralt pursues him to the kingdom of Aedirn, where Geralt is unwillingly pulled into yet another local confrontation - Aedirn's king Henselt and rebels led by Saskia. Geralt finally tracks down the assassin in Loc Muinne, where a grand summit of Northern Kingdom kings and sorceresses is taking place.
Geralt discovers that the assassins were hired by Nilfgaard to destabilize the Northern Kingdoms. Players have the choice to fight the assassin, Letho, or let him go. At the end of the game, the Nilfgaard Empire declares war on the Northern Kingdoms.
The Witcher 3: Wild Hunt
The Witcher 3: Wild Hunt concludes the story of Geralt. The war between Nilfgaard and the Northern Kingdoms is now in full swing following the events of the second game. At the same time, Geralt recovers all of his memories, and sets out to find the sorceress Yennefer, his old love. Meanwhile, the Wild Hunt - a group of Elven riders from an alternate dimension - returns to terrorize the Northern Kingdoms as they seek Ciri, Geralt's adopted daugther and witcher-in-training. Ciri's Elder Blood gives her special powers thanks to being a descendant of the Elven sorceress Lara Dorren who married a human mage after the Conjunction of Spheres, including the ability to travel between different dimensions.
Geralt must prevent the Hunt from capturing Ciri the behest of Emhyr var Emreis, the Nilfgaardian Emperor. Visibly old and tired, in a world full of danger and uncertainly, Geralt will have to fall back on his witcher instincts and experience to bring peace back to his world.