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).
Lúthien
Lúthien Tinúviel (Y.T. 1200–Y.S. 503; died aged 3377) is a fictional character in the fantasy-world Middle-earth of the English author J. R. R. Tolkien. She is an elf, daughter of Thingol and Melian. She appears in "The Silmarillion", the epic poem "The Lay of Leithian", the Grey Annals section of "The War of the Jewels", and in other texts in Tolkien's legendarium. Her story is told to Frodo by Aragorn in "The Lord of the Rings".