Source: Runeplague, pg(s). 59
The Bone Grimoire is a hundred-page tome of necromancy written in blood, and can also be used once a year as a manual for a flesh golem. A reader of the Bone Grimoire becomes undead-like as their soul becomes saturated with Zutha's influence.
The Bone Grimoire can only be destroyed with the runewaking ritual, which was designed by Sorshen near the end of Thassilon but never used before Earthfall. Doing so forces Zutha to manifest at a third of his power, and if this manifestation is destroyed before a minute passes, the entire Gluttonous Tome will be destroyed along with Zutha.
In preparation for Earthfall, Zutha divided the Gluttonous Tome into three volumes and entrusted them to his three greatest servants, instructing them to bring the pieces back once the dangers of Earthfall had passed. Thassilon's destruction was more complete than Zutha anticipated, however, and the three books were scattered to the farthest corners of Avistan.
In 4715 AR, Eando Kline—who possessed the Grimoire at the time—unwittingly helped Varian Jeggare rebuild the Gluttonous Tome while Jeggare was under Zutha's influence from the Kardosian Codex. Kline, along with Jeggare's companion Radovan Virholt, later freed Jeggare from Zutha, and together they defeated the risen runelord before he could properly reconstruct his body. They later scattered the Gluttonous Tome again, but this brief return was enough for Zutha to re-establish a foothold in the world and for his influence to fester within all of its fragments.
While the other two pieces remained hidden, the Bone Grimoire fell into the hands of Leptonia, a half-drow cleric of Yamasoth, who used it as payment for the service of the dhampir necromancer Erigantus in crafting the polymorph plague. Erigantus took the Bone Grimoire to Kaer Maga and studied it, eventually finding a way to destroy the seal in the Shrine of the Seal. Armed with this knowledge, Erigantus assaulted the Shrine of the Seal and slaughtered its guard, removing one of the two seals that was keeping Tar-Baphon imprisoned.
The Bone Grimoire and its reunification with the other Gluttonous Tome volumes are central to the plot of Lord of Runes.
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