The Book of the Dead, believed to be one of eight divine relics somehow central to the integrity of reality itself. Anything which touches it is cursed by (un?)death. Naming a creature and writing its name in the book dooms them to die.
Once locked in the treasure vault of Dominic Tremere, the Necronomicon was then arranged to be stolen by the medusa Pulchritudinous Euryale and traded to the ex-druid Isis Ra’ksh in exchange for a potion to restore Euryale’s humanity.
Once in Isis’s possession, she used it to poison the Yggdrasil in a misguided effort to counter a nebulous world-destabilizing force she called the Vortex. But the Book’s evil took root within Isis, festering into the parasitic entity Zuggtmoy, before jumping to the Fae Queen. When this happened, Isis came to her senses and discarded the Necronomicon in horror at what she had done.
Elven scouts recovered the discarded Book and locked it away in the royal treasury; the SPI infiltrated the treasury and aided Sartus Morningdew in invoking a miracle, the pinnacle of mortal magic, to erase the writings in the Book, cleansing its corruption at the source.