The Doors of Oerth
Ancient legends relate that an evil sorcerer named Azirian once summoned a black ship from a distant land far across the ocean, a ship loaded with a cargo of terrifying artifacts, among them the Cryptichronos (also known as The Hidden Time, in reference to its ancient origins, and as The Book of Horrors, for more obvious reasons). Scholars agree that Azirian must have gone insane when he read the grimoire, for he tried to use its powers to summon a beast he claimed could destroy the world, then fled with the book into the earth’s catacombs, where he surrendered his will (and his body) to the hunger of the illithids.
No more is known of the Cryptichronos until it is mentioned 500 years later in the journals of the wandering mage Adjazzet, who discovered the book in a rusted, subterranean vault and managed to record some of the book’s contents before also going mad, committing suicide by ingesting green slime. His apprentice Olmoroth inherited the work and used it to become the tyrannical ruler of a dying city; however, he eventually lost the book (and his life) in a necromantic duel with a vastly superior opponent, possibly a beast from the lower planes.
The book reappears again, in 513 CY, in the Splendelowe Lake Valley when a group of adventurers were sent into the lost city of Aluvas to retrieve it. What became of those adventurers no one knows. Somehow it ended up on the Fading Lands known as the Isle of Dread where it was buried in a chest with a large amount of gold coins by the Pirate Ricard.
The present whereabouts of the Cryptichronos remain unknown, and wise men fear that the book may have fallen into wicked hands. Anyone finding the grimoire is encouraged to destroy it for fear of someone unleashing an unspeakable horror upon the world. Indeed, this latter possibility may have already happened in the campaign world.