Screwtape is a dedicated devil and the author of all the letters that appear in the novel. He is committed to enticing as many souls as possible to sin, damnation, and Hell. As the novel progresses, and especially in the Epilogue, it emerges that Screwtape eats the dead who are damned, enjoying the tastiness of their sins.

Despite being a villainous character, Screwtape is an experienced observer of human nature and behavior. Much more than Wormwood, he grasps Humans as Both Physical and Spiritual Beings and consequently understands how it is that human beings are attracted to either virtue or vice. As a demon, he has many strategies to tempt his “patients” to choose the latter and is particularly articulate on the subjects of pride and lust, though he personally most embodies the sin of gluttony.

Screwtape is also a keen observer of the “Enemy”: God. Screwtape often writes in philosophical ways about the spiritual conflict between Heaven and Hell, but his cynicism about both humanity and God at times clouds his reasoning. For instance, Screwtape is perplexed by The Role of Reason and Free Will in Christian Life, failing to appreciate (at least on an emotional level) why God would grant humanity free will rather than merely force them to behave virtuously.