Tome of the Unknowable

Wondrous item, legendary

This hefty tome is filled with a thousand ancient pages of incomprehensible text from multiple dead languages. Reading the book serves no purpose, as its texts are indecipherable even with the aid of magic. A warlock gains a +3 bonus to any Intelligence check or Intelligence saving throw it makes while the book is on its person.

Holding the book fills a person with the same sense of dread as standing on the edge of a cliff, which a creature holding the book can use an action to mentally jump from. When it does, that creature must make a DC 15 Intelligence saving throw. On a failed save, the creature takes 6d8 psychic damage and is stunned for 1 minute. This damage can't be reduced in any way, and the condition can't be prevented or ended early. On a success, the creature then gains the benefits of either the contact other plane or legend lore spell (its choice each time); it doesn't make the saving throw again as part of the contact other plane spell in this way. The save DC for this property increases by 1 each subsequent time it's used after the first, resetting to 15 again daily at dawn.

Curse. This book is cursed, which can only be detected by a legend lore spell. A creature that rolls a 1 on the saving throw when using the book's properties becomes cursed by it. Only a greater restoration spell or similar magic can end this curse. Each day at dawn, a creature cursed in this way suffers a cumulative −1 penalty to any Intelligence check or Intelligence saving throw it makes. If the penalty drops to −10, the creature's Intelligence score is reduced to 1, and it is incapacitated until the curse is ended.

Vasily quietly entered his bookstore from the back, trembling with the excitement of what he carried in his pack. He would have to thank Galvez for the nice tip on recognizing Dantly's library. It was there, in the bowels of the archmage's wild domain, that he found it.

His shifty warlock buyer would be very pleased indeed.

Vasily gently placed the book on his desk, and slowly unwrapped the protective cloth. The little owl brooch on his chest hooted with delight as the last of the cloth fell to the side and revealed the heavy tome. Touching its cover filled him with morbid curiosity—was it true what they said about its pages? Should he try it out for himself? To see if his buyer was getting his money's worth, of course.

With trepidation, Vasily opened the book to a random page and immediately felt it. A heavy weight of anxiety gripped him. He looked down and could see the world spinning, see the pages transforming into the starry void, and felt himself pitching forward.

The sensation ended with a snap as he closed the book shut. "Nope," he said decisively, and put the book under the counter.