Scene described in 'The tower of the swallow' book. Geralt meets Avallac'h in Gorgon cave.
Looking for information about Ciri, Geralt was sent into the cave by Regis, at the guidance of a flaminica druid. He had to enter the cave unarmed. ''The Witcher, not being a sorcerer, must prove himself capable of humility and sacrifice. He must enter into the dark depths of the earth. Disarmed. Abandoning all weapons, any sharp iron. All evil thoughts. And aggression, rage, anger or pride. He must enter with humility.''
He did not know who he will meet in the cave, he only was told that there is a person who knew where Ciri was.