The Rites of the Moon is an item introduced in Legend of Grimrock 2. Formerly the property of Jakon Riddle, it is bequeathed to anyone who solves his final puzzle and finds its Treasure Chest in the Cemetery.
The effect of reading the book is not specified; upon reading it, a message reading only "[Character] is somehow changed." will appear. A character who reads this will, during the night, gain 5 points in Vitality (consequently gaining 25 Health and 10 Poison Resistance). During the day, however, they will lose 5 points in Vitality, and suffer the accompanying losses to Health and Poison Resistance. In-game data refers to the character who has read the book as a "Nightstalker", though the title of this trait is not displayed on the character panel.