The book collects fourteen short stories by various authors, with an introduction by the editor. All share the Cthulhu Mythos setting originated by H. P. Lovecraft, but unlike his stories, which generally take place in modern times, are set in previous historical eras. The effect is to take the Mythos from the realm of contemporary horror into that of historical fiction. The stories are presented in chronological order from the 2nd millennium BC to the late 19th century, with the last set in the present but looking back to medieval events.