The definitive treatise on all that is good in the multiverse, the fabled Book of Diancecht figures prominently in the lore of Diancecht. 

A heavy clasp, wrought to look like angel wings, keeps the book’s contents secure. Only a devout creature of Diancecht that is attuned to the book can release the clasp that holds it shut. Once the book is opened, the attuned creature must spend 80 hours reading and studying the book to digest its contents and gain its benefits. Other creatures that peruse the book’s open pages can read the text but glean no deeper meaning and reap no benefits. An evil creature that tries to read from the book takes 24d6 radiant damage. This damage ignores resistance and immunity, and can’t be reduced or avoided by any means. A creature reduced to 0 hit points by this damage disappears in a blinding flash and is destroyed, leaving its possessions behind.

Benefits granted by the Book of Diancecht last only as long as you have this book. If you behave in a way that displeases Diancecht you lose all the benefits granted by the book until you prove your faith.

Random Properties 

The Book of Diancecht has the following random properties:

• 2 minor beneficial properties
• 2 major beneficial properties

Increased Wisdom

After you spend the requisite amount of time reading and studying the book, your Wisdom score increases by 4, to a maximum of 24. You can’t gain this benefit from the book more than once.

Enlightened Magic

Once you’ve read and studied the book, any spell slot you expend to cast a cleric or paladin spell counts as a spell slot of one level higher.

Halo 

Once you’ve read and studied the book, you gain a protective halo. This halo sheds bright light in a 10-foot radius and dim light for an additional 10 feet. You can dismiss or manifest the halo as a bonus action. While present, the halo gives you advantage on Charisma (Persuasion) checks made to interact with good creatures and Charisma (Intimidation) checks made to interact with evil creatures. In addition, fiends and undead within the halo’s bright light make attack rolls against you with disadvantage.

Destroying the Book

It is rumored that the Book of Diancecht can’t be destroyed as long as good exists in the multiverse. However, drowning the book in the River Styx removes all writing and imagery from its pages and renders the book powerless for 1d100 years.

Notes: Bonus: Wisdom Score, Bonus: Ability Score Maximum, Spell Slot Increase: Cleric, Spell Slot Increase: Paladin, Advantage: Persuasion, Advantage: Intimidation, Creature of Diancecht faith. , Damage, Buff, Utility