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).
Christopher Tolkien
Tolkien had long been part of the critical audience for his father's fiction, first as a child listening to tales of Bilbo Baggins (which were published as "The Hobbit"), and then as a teenager and young adult offering much feedback on "The Lord of the Rings" during its 15-year gestation. He had the task of interpreting his father's sometimes self-contradictory maps of Middle-earth in order to produce the versions used in the books, and he re-drew the main map in the late 1970s to clarify the lettering and correct some errors and omissions. J. R. R. Tolkien invited Christopher to join the Inklings when he was twenty-one years old, making him the youngest member of the informal literary discussion society that included C. S. Lewis, Owen Barfield, Charles Williams, Warren Lewis, Lord David Cecil, and Nevill Coghill.