Screwtape is the central tempter who writes the letters in C.S. Lewis’s The Screwtape Letters.
The book is structured as a series of letters from Screwtape, an experienced demon, to his junior colleague Wormwood. Screwtape gives advice about tempting a human being, whom he calls “the Patient,” while Lewis uses the demonic viewpoint to satirize human weaknesses.
Lewis wrote the work during the Second World War. The letters first appeared in the Anglican newspaper The Guardian in 1941, and the complete book was published that same year. Its unusual reversal—presenting moral instruction through a demon’s advice—made it distinctive among Christian apologetic works.
Wormwood is therefore not the answer: he is the younger demon receiving the letters. The book’s sequel, Screwtape Proposes a Toast, was published separately in 1959.