Screwtape is the senior demon who gives advice in C.S. Lewis’s The Screwtape Letters.
The 1942 book is structured as a series of letters from Screwtape to his younger nephew Wormwood. Screwtape advises Wormwood on tempting a human patient, while Lewis uses the demonic correspondence to satirize human weakness and expose distorted moral reasoning.
Lewis wrote the letters as a work of Christian apologetics, but their format is deliberately indirect. The reader sees human behavior through the perspective of an enemy of God, allowing Lewis to make irony do much of the argumentative work.
Wormwood is the junior demon and recipient, not the answer. The title character and letter writer is Screwtape, whose confident advice repeatedly reveals the absurdity of the demonic viewpoint.