The witcher trials are primarily a series of three grueling stages in the witcher training process. First comes The Choice, which involves dietary changes and grueling physical training. Young witchers are taught sword skill, monster lore and herbalism. The main trials are as follows:
- The Trial of the Grasses, which involved consuming various alchemical ingredients, or "the grasses" and affected the nervous system,
- The Trial of the Dreams, which involved the mutation of the eyes, bone marrow and hormones, allowed for better night vision, among other benefits. It also resulted in infertility.
- The Trial of the Mountains
Due to his remarkable resilience to the "normal" trials, Geralt was also subjected to additional, even more experimental trials, hence his superior abilities and also his white hair.
"The procedure lasted several days. Over that time we were given magical mutagenic potions that completely altered our metabolism. Then we awaited the effects, which usually were unrelentingly awful. Nonstop fevers, vomiting, hemorrhages ... Yes, not all rumors about the witcher order are mistaken, and at this point the cull was indeed very severe. The vast majority of those undergoing the trial did not live past this phase.
- The few who did moved on to the next part-the Changes. At this stage we were given further infusions and potions, infected with filth of some kind ... And again came fever, sweat, delusions, shit, and vomit beyond reason. Supposedly the process was "enhanced" from time to time, as a test of new elixirs and mutagens. Typically this meant even more pain, vomit, or worse for those chosen for these "special trials." Geralt emerged from these experiments with a lifetime of foul memories and the loss of pigment in his hair. The other members of that particular test group were not so lucky- not one of them survived."
- pg. 57, The World of the Witcher