In the Unwanteds Quests: Dragon Captives, it is shown that Fifer (along with Thisbe) are the main characters in the book, ten years after the Island of Dragons book.
Fifer Stowe grew up alongside her twin sister, Thisbe Stowe. They were and always had been inseparable. She and Thisbe got into a lot of trouble constantly, so Alex deprived them of learning anything that could expand their magic ability. This made life difficult, since Fifer always wanted to learn magic but never was allowed.
Fifer is much calmer than her sister. She likes adventure and taking risks. She is the more reasonable twin, and uses logic and her heart to make decisions. She is nicer and less of a worrywart than Thisbe. She is fearless, unafraid of everything except Alex's rules and temper. She compares herself to Thisbe a lot and doesnt believe she has much of a chance at anything compared to her twin sister. When left alone to fix the dragon wings, Fifer doesnt know what to do without Thisbe and feels helpless and dumb.
Fifer has long curly black hair and black eyes. Because her mom was Morocoon/African and dad was Italian, she passes as half-white. She has a darker skin tone than Alex and Aaron.