Tales of lore tell of the Book of Eibon, a tome so ancient that it was originally written in the Hyperborean language of Tsath-Yo, long before Atlantis was born from the sea. It goes by dozens of names and predates even the Necronomicon and Unaussprechlichen Kulten. Now, Chaosium reveals the true secrets of the Book of Eibon for the first time.

The contents of the Book of Eibon are primarily the work of Clark Ashton Smith, one of the most famous authors of Weird Tales and the inventor of the Book of Eibon, as well as Lin Carter, esteemed fantasy and horror editor. Robert Price, Richard L Tierney, Joseph Pulver, and a number of other authors have helped complete the text, resulting in a tome that reveals all the secrets of the Cthulhu Mythos, from the history of the first alien races to come to Earth, to the histories of the Elder Magi of Hyperborea, and the story of Eibon's life and death.