Cathryn C. Holister is a satirist and author of fantasy books. Her stories about two chaotic demon girls messing up hell's top management have been previously released in five books; the anthology series "Demon's Diaries" and two novels, "Inferno for Beginners" and "Inferno, Chaos and Conspiracies", both published by Periplaneta Verlag Berlin. All of Cathryn's books are richly illustrated, with the two novels, she also developed an augmented content app. Triggered by the illustrations the app reveals virtual content, e.g. additional texts, audio and comics.