A book created by the First Necromancer. This massive tome contains the secrets, experiments, and knowledge of how Life, Death, Undeath, Magic, and Negative energy coalesce. Such knowledge would likely drive one into the pits of despair and obsession. The spirits within constantly whisper and scream, urging you to read deeper into the book and attune to it. 

Other practitioners of evil have held the book and added their own input to its catalog of vile knowledge. The cost of this obsession binding their souls to the book. With each soul captured, a new page is added. With new knowledge and unholy sorceries to be practiced by the next unlucky reader.

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.

Spirits despise the book as it drags them towards it like a whirlpool. Any spirit type fey or undead, or any living creature under the effect of the Astral Projection spell within 30ft of the book must make a DC 20 wisdom save or be trapped inside the book.

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 the reach of undeath, and expand the lore already contained within.

Whenever a non-evil creature attunes to the Tome of a Thousand Souls, that creature must make a DC 17 Charisma saving throw. On a failed save, the creature’s alignment changes to neutral evil.

The Tome of a Thousand Souls remains with you only as long as you strive to work undeath into the world. If you fail to perform at least one evil act within the span of 10 days, or if you willingly destroy any undead creature, the book disappears. If you die while attuned to the book, the book claims your soul. You can’t be restored to life by any means while your soul remains imprisoned.

Random Properties. The Tome of a Thousand Souls has the following random properties:

• 3 minor beneficial properties
• 1 major beneficial property
• 3 minor detrimental properties
• 2 major detrimental properties

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 undeath. An evil rune might appear on your face, your eyes might become glossy black, or your skin may appear pale or decayed. Or you might become wizened and hideous, lose all facial features, gain a thirst for humanoid blood, 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.

Negative Feed. While you are attuned to the Tome of a Thousand Souls, you add the Undead tag to your creature type and are effected by any spell or ability that would target the undead. You become immune to necrotic damage and vulnerable to radiant damage. Healing magic also becomes detrimental as any positive energy damages you and negative energy empowers you. Should you become the target of a healing spell, you instead receive damage equal half the total HP recovered by the spell. Any time you receive necrotic damage, you are instead healed by that number.

Command Death. While you are attuned to the book and holding it, you can use an action to cast the dominate monster spell on any undead target (save DC 19). You can’t use this property again until the next dawn.

Dark Lore. You can reference the Tome of a Thousand Souls 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.

Spirit Sight. While you are attuned to the Tome of a Thousand Souls, you can see into the ethereal plane.

Dark Speech. While you carry the Tome of a Thousand Souls and are attuned to it, you can use an action to recite words 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 Tome of a Thousand Souls 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 × 100 years later.

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

Vile Lore

The Tome of a Thousand Souls touches on every undead in the cosmos. A character can use the lore the book contains to unearth terrible secrets no mortal should know. Among the contents a character might find are the following, plus whatever else you choose:

• Vile Apotheosis. The book could hold a ritual that allows a character to become a lich, death knight, skull lord or mummy lord.
• True Names. The true names of any number of fiends might be in the book.
• Dark Magic. Several spells of horrific evil of the DM’s design and choosing could be in the book. Spells could impose dreadful curses, disfigure others, require human sacrifice, afflict creatures with crippling pain, spread vile plagues, enslave ghosts and specters, and so on.

Notes: Advantage: Persuasion, Advantage: Intimidation, Expertise: Intelligence Ability Checks, requires attunement by a bar, sorcerer, wizard or warlock, Damage, Control, Buff, Debuff, Utility, Combat, Cursed