C. S. Lewis
Lewis and fellow novelist J. R. R. Tolkien were close friends. They both served on the English faculty at Oxford University, and were active in the informal Oxford literary group known as the Inklings. According to Lewis's memoir "Surprised by Joy", he was baptised in the Church of Ireland, but fell away from his faith during adolescence. Lewis returned to Anglicanism at the age of 32, owing to the influence of Tolkien and other friends, and he became an "ordinary layman of the Church of England". Lewis's faith profoundly affected his work, and his wartime radio broadcasts on the subject of Christianity brought him wide acclaim.
Mount Doom
Reviewer Bart Higgins noted the similarity between Tolkien's Mount Doom and the volcanic caverns under Venus depicted in "Perelandra" by Tolkien's friend C.S. Lewis. "In both cases, the book reaches a cataclysmic scene of a struggle in an underground cavern, ending with an evil being falling into volcanic fire and being consumed. Since it is well known that Tolkien and Lewis frequently shared with each other their respective works in progress, it is reasonable to assume that the resemblance is no coincidence".