The Citadel of Fear is a science fiction lost race novel by Francis Stevens (pseudonym for Gertrude B. Bennett), The woman who invented dark fantasy . This lost world story focuses on a forgotten Aztec city, which is rediscovered during World War I. Two adventurers discover a lost city in the Mexican jungle. One is taken over by an evil god while the other falls in love with a woman from the ancient Mexican city of Tlapallan. The Citadel of Fear is considered Francis Stevens masterpiece, by Lovecraft s acclaim. The Citadel of Fear was first published as a serial in Argosy Magazine in 1918-1919. It was eventually republished as a novel in 1970. It is now considered a lost classic . Gertrude Barrows Bennett (1883-1948) was the first major female writer of fantasy and science fiction in the United States, publishing her stories under the pseudonym Francis Stevens. Bennett wrote a number of highly acclaimed fantasies between 1917 and 1923 and has been called the woman who invented dark fantasy . Her most famous books include Claimed! (which Augustus T. Swift, in a letter to The Argosy called One of the strangest and most compelling science fantasy novels you will ever read ) and the lost world novel The Citadel of Fear. Bennett has been credited as having the best claim at creating the new genre of dark fantasy . It has been said that Bennett s writings influenced both H. P. Lovecraft and A. Merritt, both of whom emulated Bennett s earlier style and themes .