This book is given to YGGDRASIL players, so as to let them understand the basic functions of the game. It is a unique item that was impossible to take by force unless the owner gave it away voluntarily. This was an item that reflected the developer's intention of turning mysteries into exploration.
It's a heavy tome with easily over a thousand pages long.
This book acted as an journal for YGGDRASIL players. Once a player encountered a new monster, the Encyclopedia automatically recorded its basic data. However, the detailed stats were not recorded, only the name, appearance, and the myth behind them. If one wanted to fully utilize the potential of this item, they needed to investigate the monster's weaknesses or special abilities themselves and manually enter them into the book.