: A fierce protector sent by January's father. Originally from a world where women are hunters, she becomes January's most vital ally.
: The story alternates between January's present-day struggle for freedom and the book-within-a-book, which recounts the epic love story of Adelaide Lee Larson and Yule Ian Scholar (January’s parents) across different dimensions.
: The primary antagonist and January's guardian. He is revealed as a centuries-old exile from another world who seeks to "civilize" the world by closing all portals.
: On her seventeenth birthday, January finds a leather-bound book titled The Ten Thousand Doors , which contains academic studies and stories of portals between worlds.