The Trial of the grasses or herbs was an incredibly painful trial which young witcher apprentices were subjected to. It required the consumption of special alchemical ingredients known as "the grasses" and affected the physiology of the subject.
Reportedly, only three in ten survived the trial, those who didn't survive died in agony, but those who did gained lightning quick reflexes, their signature cat-like eyes, and other bodily enhancements in return. The latest trial was performed at Kaer Morhen during the events of The Witcher 3: Wild Hunt.
"On the third day all the children died save one, a male barely ten. Hitherto agitated by a sudden madness, he fell at once into deep stupor. His eyes took on a glassy gaze, incessantly with his hands did he clutch at clothing, or brandish them in the air as if desirous of catching a quill. His breathing grew loud and hoarse; sweat cold, clammy and malodorous appeared on his skin. Then he was once more given elixir through the vein and the seizure it did return. This time a nose-bleed did ensue, coughing turned to vomiting, after which the male weakened entirely and became inert.
- For two days more did symptoms not subside. The child's skin, hitherto drenched in sweat, grew dry and hot, the pulse ceased to be full and firm — albeit remaining of average strength, slow rather than fast. No more did he wake, nor did he scream.
- Finally, came the seventh day. The male awoke and opened his eyes, and his eyes were those of a viper..."
- pg. 77, Blood of Elves (UK edition)
Though another lab can be found outside the castle and inside a cave to the south, in Witcher 3 Wild Hunt, the player can explore this lab during the scavenger hunt for Wolf School gear and Geralt will reminisce about his past subjection to the chemicals.
During the quest Va Fail, Elaine, Geralt needs to brew the Decoctions of the Grasses. The witchers and Yennefer then subject Uma (Avallac'h) to the first part of the Trial. This consists of administering Mother's Tears, Wildrye Juice, and Speargrass Sap into the veins.
- In the video game, it is during this trial that Geralt's hair is said to have turned completely white. In the books, however, Geralt's hair turned white as a side effect of some "additional experiments" which were performed on him. However both are true due the fact that the ones experimenting on Geralt modified his traits.
- "Trial of the Herbs" is the title of a song by Marcin Przybyłowicz included on the Inspired by The Witcher CD.