Geralt was born in 1174 as the son of the sorceress Visenna and presumably the warrior Korin. Shortly after his birth, his mother left him at the School of The Wolf in the stronghold of Kaer Morhen where he was made and trained to become a Witcher. As a child, he was subjected to the Trial of The Grasses, (of which only 3 out of 10 survive). Geralt survived the many blistering mutations required to grant Witchers their abilities. After displaying unusual tolerance, Geralt was selected to further experimental mutations which granted him considerably greater strength, speed, endurance, resilience, healing, senses, complete immunity to diseases and conventional poisons, and extreme resistance to pain. Geralt was the only witcher to survive these experiments. This resulted in his hair turning white and received the nickname ‘White Wolf’.
He was trained by his mentor Vesemir whom he came to regard as a father-figure. Geralt underwent many years of rigorous training with one infamous obstacle course known as ‘The Pendulum’. He soon met his fellow classmate Eskel and the two became good friends, almost as close as brothers. One time they captured a large forest bumblebee and tied it to a jug. The pair laughed at its antics until they were discovered by Vesmeir who punished them with a leather strap. He also befriended Lambert and Coën. As young witcher's were encouraged to make surnames for themselves in the interest of appearing trustworthy towards their clients, Geralt initially chose the name "Geralt Roger Eric du Haute-Bellegarde" however this was regarded as silly and pretentious by Vesemir, and so instead he chose the name 'Rivia' and even adopted a Rivian accent to make himself sound more authentic. Geralt also spent time training with Mother Nenneke at the Temple of Melitele in Ellander.