Pandemonicon is an ancient, sentient tome of demonology originally inscribed by the sorcerers of the Tower of Babel in Babeleth Darklands, as dictated to them by a dark angel in an attempt to give the mortals a way to fight demons. However, the book became distorted and corrupted by the evil forces it was supposed to repel. It speaks in echoing whispers to draw people to it, but it can only be properly read and understood by those it deems worthy. It has been copied in the past, but most of those copies have been lost in time.
One copy exists in the library of Heroica after it was uncovered from a Temple of Zoot, where it was brought by Sycamore Ziegfried. The copy had been in the possession of the Ziegfried family for countless generations.
Another copy was recently taken by a mysterious man with a wide-brimmed hat from the ziggurat of the lost land of Azzurat that got buried under a desert. An old hag had given it to King Nebukadnezzar decades ago, and the king's hunger for power and fame caused him to summon demons with the help of the book and ultimately doom his kingdom.
A third copy was given to the Green Witch of Ozmath over a thousand years ago. Through that copy, the archdemon Rosier was summoned to the mortal realm, but s/he was bound to the Lost Forest by other witches, unable to escape. The fate of that copy of Pandemonicon is currently unknown.