Elwin Ransom
Elwin Ransom may be based on C. S. Lewis' friend J. R. R. Tolkien ("Elwin" means "Elf friend" in Anglo-Saxon), though he seems to have autobiographical elements. In "That Hideous Strength" Ransom, with his royal charisma and matter-of-fact breezy acceptance of the supernatural, appears less like Tolkien than like Charles Williams (or some of the heroes in Williams' books).
J. R. R. Tolkien
Tolkien's devout Roman Catholic faith was a significant factor in the conversion of C. S. Lewis from atheism to Christianity, although Tolkien was dismayed that Lewis chose to join the Church of England.