C. Freston is the name of the figure Don Quixote believes to be his greatest enemy.
When Cervantes wrote The quixote he expected to put an end to the knight novel, by creating an imaginary enemy that ridiculized all enemies in novels, Don quixote trhough the novel believes that Freston stole his books and turned the giants into windmills, making him look bad. He is kind of a magician/wiseman.