Screwtape is the senior tempter who writes the letters in C.S. Lewis’s The Screwtape Letters.
The book was published in 1942 and takes the form of advice from Screwtape to his inexperienced nephew, Wormwood. The letters discuss how demons might tempt a human being, whom Screwtape calls “the Patient,” away from faith and moral discipline.
Lewis presents the book as a satirical inversion of spiritual instruction. The narrator’s demonic perspective lets Lewis examine pride, distraction, self-deception, resentment, and other weaknesses without presenting the advice as morally trustworthy.
Wormwood is the junior tempter receiving the letters, so he is not the answer to the question about the writer. The title refers to the correspondence of Screwtape, the experienced bureaucrat of Hell who gives the guidance.