Source: Keys from the Golden Vault

Wondrous item, Artifact (Requires Attunement)

The contents of this foul manuscript of ineffable wickedness are the meat and drink of those in evil's thrall. No mortal was meant to know the secrets it contains, knowledge so horrid that to even glimpse the scrawled pages invites madness.

Most believe the lich-god Vecna authored the Book of Vile Darkness . He recorded in its pages every diseased idea, every unhinged thought, and every example of blackest magic he came across or devised. Vecna covered every vile topic he could, making the book a gruesome catalog of all mortal wrongs.

Other practitioners of evil have held the book and added their own input to its catalog of vile knowledge. Their additions are clear, for the writers of later works stitched whatever they were writing into the tome or, in some cases, made notations and additions to existing text. There are places where pages are missing, torn. or covered so completely with ink, blood, and scratches that the original text can't be divined.

Nature can't abide the book's presence. Ordinary plants wither in its presence, animals are unwilling to approach it, and the book gradually destroys whatever it touches. Even stone cracks and turns to powder if the book rests on it long enough.

A creature attuned to the book must spend 80 hours reading and studying it to digest its contents and reap its benefits. The creature can then freely modify the book's contents, provided that those modifications advance evil and expand the lore already contained within.

Whenever a non-evil creature attunes to the Book of Vile Darkness , that creature must make a DC 17 Charisma saving throw. On a failed save, the creature's alignment changes to neutral evil.

The Book of Vile Darkness remains with you only as long as you strive to work evil in the world. If you fail to perform at least one evil act within the span of 10 days, or if you willingly perform a good act, the book disappears. If you die while attuned to the book, an entity of great evil claims your soul. You can't be restored to life by any means while your soul remains imprisoned.

Circle of Death. While attuned to the book, you can cast Circle of Death (save DC 20) from it as an action. After you cast the spell, roll a d6. On a roll of 1-5, you can't use this property again until the next dawn.

Condition Immunities. While attuned to the book, you can't be charmed or frightened.

Evil Presence. The book houses an evil spirit that is hostile toward you. When you become attuned to the book, the spirit tries to leave the book and enter your body. If you fail a DC 20 Charisma saving throw, it succeeds, and you become an NPC under the DM's control until the intruding spirit is banished using magic such as the Dispel Evil and Good spell. The banished spirit returns to the book.

Adjusted Ability Scores. After you spend the requisite amount of time reading and studying the book, one ability score of your choice increases by 2, to a maximum of 24. Another ability score of your choice decreases by 2, to a minimum of 3. The book can't adjust your ability scores again.

Mark of Darkness. After you spend the requisite amount of time reading and studying the book, you acquire a physical disfigurement as a hideous sign of your devotion to vile darkness. An evil rune might appear on your face, your eyes might become glossy black, or horns might sprout from your forehead. Or you might become wizened and hideous, lose all facial features, gain a forked tongue, or some other feature the DM chooses. The mark of darkness grants you advantage on Charisma (Persuasion) checks made to interact with evil creatures and Charisma (Intimidation) checks made to interact with non-evil creatures.

Command Evil. While you are attuned to the book and holding it, you can use an action to cast the Dominate Monster spell on an evil target (save DC 18). You can't use this property again until the next dawn.

Dark Lore. You can reference the Book of Vile Darkness whenever you make an Intelligence check to recall information about some aspect of evil, such as lore about demons. When you do so, double your proficiency bonus on that check.

Dark Speech. While you carry the Book of Vile Darkness and are attuned to it, you can use an action to recite word from its pages in a foul language known as Dark Speech. Each time you do so, you take 1d12 psychic damage, and each non-evil creature within 15 feet of you takes 3d6 psychic damage.

Destroying the Book. The Book of Vile Darkness allows pages to be torn from it, but any evil lore contained on those pages finds its way back into the book eventually, usually when a new author adds pages to the tome.

If a solar tears the book in two, the book is destroyed for 1d100 years, after which it reforms in some dark corner of the multiverse.

A creature attuned to the book for one hundred years can unearth a phrase hidden in the original text that, when translated to Celestial and spoken aloud, destroys both the speaker and the book in a blinding flash of radiance. However, as long as evil exists in the multiverse, the book reforms 1d10 x 100 years later.

If all evil in the multiverse is wiped out, the book turns to dust and is forever destroyed.