The Tome of Fistandus rose from the depths of obscurity in the hands of the Dreadmage Fistandus, but it's origins are from far before that. The large black book, bound in leather that cannot be penetrated by even a magical blade nor burnt by dragonfire, was originally the property of the Planar Sailors. It was written as an archive of all the magical knowledge the demigods possesed. The book was then lent to the first king of the gnomes, who used it to carve out the great city of Dragonmourne in the far northern regions of the world, and later used in an attempt to defeat the demon lord Denair who in turn took the book, and was enslaved by the summoning magics of Fistandus, forfeiting the book to the conjurer.
As the book progresses, the magic formulae decay into more lesser known and archaic languages, while the magics become more and more powerful. The final inscriptions are written in the tongue of the gods themselves, unable to be translated even by it's writers, the words merely put into their minds by some deific whim to be written down. The formulae directly before the ones written in the back of the book are written in the language of the Planar Sailors themselves, which is incomprehensible to beings of the Prime Material Plane unless some magical artifact allows them to decode it.