What is the Trial
The Trial of the Grasses is the defining process that creates a witcher. Young apprentices are subjected to a combination of mutagenic herbs, virus cultures, and alchemical compounds that alter their physiology. The process is excruciating, takes approximately one week, and kills the majority of candidates.
The Procedure
The trial begins with an initial phase where certain herbs are administered via teas to prepare the body. The main phase involves herbs and elixirs injected directly into the veins of immobilized children. The specific substances include corn lily, nightshade, speargrass, wildrye, and wolfsbane.
Most apprentices die by the third day. Survivors experience bouts of sudden madness before falling into a deep stupor, their eyes turning glassy, hands grasping at nearby clothing, breathing loud and hoarse. The entire ordeal lasts roughly a week before the body either accepts or rejects the mutations.
Survival Rate and Mutations
Only about three out of ten boys survived the standard trial. Survivors gained several permanent mutations: cat-like yellow eyes with vertical pupils, dramatically enhanced reflexes, sharpened senses (smell, hearing, sight), increased physical strength and endurance, slower aging, and resistance to toxins that would kill normal humans.
The mutations also carried costs. Witchers became infertile and experienced a diminished emotional range (though the extent of emotional suppression is debated in both the books and games). Many witchers report feeling emotions but have been trained to suppress them.
Geralt of Rivia underwent additional experimental mutations beyond the standard trial, which no other witcher is known to have survived. These gave him greater resilience but also caused him to lose all hair pigmentation, resulting in his white hair.
Historical Context
The Trial of the Grasses was developed centuries before the events of the games. Knowledge of how to perform the trial was closely guarded by each witcher school. After mobs and mage-led attacks destroyed several schools, this knowledge was progressively lost. In The Witcher 3, Vesemir (the oldest surviving witcher) stated that the knowledge needed to create new witchers had been lost along with Kaer Morhen's laboratories. The Witcher IV complicates that claim by depicting Ciri's Trial of the Grasses.
Ciri and the Trial
In the books and previous games, Ciri never underwent the Trial of the Grasses. She trained at Kaer Morhen as a swordfighter but was never subjected to the mutations. The Trial was historically administered only to boys, and it was widely believed that girls could not survive it (though the School of the Cat was known to accept female trainees).
In The Witcher IV, Ciri has clearly undergone the Trial. Her cat-like eyes, ability to use witcher signs, and consumption of witcher potions all confirm the mutations took hold. How she survived a process that kills 70% of male candidates and was considered impossible for women remains an open question. Her Elder Blood, her status as a Source (someone born with innate magical talent), and her extensive training under Yennefer likely played a role.
Game director Sebastian Kalemba confirmed that players will experience Ciri's Trial of the Grasses firsthand during the game, witnessing her transformation. This makes it one of the most anticipated narrative sequences in The Witcher IV.