Elder Casian:
You are looking for Chapter 4 of the sacred scripture? That is not something that I can hand over easily. Do you know what the scripture contains? Nothing less than all the knowledge of the world!
This book may yet reveal the lost knowledge and science of the Giants, who have long since vanished from this world. Oh, the ultimate secrets of geometry... I lack the rest of chapters 1, 2 and 3, so many details are still unknown to me.
Tell him that you will show him chapter 1, 2 and 3 if he shows you chapter 4.