Tome of Iltkazar

A legendary grimoire that once belonged to the ancient "Mage-King" of Iltkazar, a realm of eastern Calimshan that had vanished hundreds of years ago. This tome is said to contain many spells, like those of Illefarn, found nowhere else, including a means of creating a permanent gate between the planes of existence, and the means to create golem armies.

Official campaign
The tome had been in the possession of the Arcane Brotherhood, but they were forced to give it to Ruathym as part of the terms of a peace treaty. This did not sit well with them, and when Black Garius stole the grimoire for his own goals, Luskan and Ruathym quickly were back at war.

Because most of the Arcane Brotherhood were focused on the war, Garius was able to operate behind their backs and work on his ritual to assimilate the King of Shadows' power. In addition he used it to reactivate various blade golems.

The ritual had been disrupted and only turned him and other ritualists into Shadow Reavers, but they managed to hold on to the Tome. Eventually, the PC retrieved the tome from a Reaver, and Aldanon used it to devise a portal directly into Merdelain.