Carmen Thomas was born in Londonderry, Ireland, to two Hogwarts graduates. Her parents, Deirdre and Liam, both worked in different fields- her mother has spent years at St. Mungo's as a healer and her father works as an Archivist of wizarding history. She grew up fully aware of the wizarding world, waiting patiently for her own chance to attend Hogwarts. She attended a muggle primary school after she was old enough to know not to talk about the wizarding world, and befriended Emily, a muggle who she grieved over leaving behind when she was accepted to Hogwarts.

When she was seven years old, the first of her powers surfaced. She was in an argument with her mother when her annoyance overwhelmed her and she accidentally shattered an old teapot that was sitting on the stove, without ever touching it. She doesn't quite remember what the argument was about, but she remembers the joy on her mother's face when she realized what had happened.

Carmen, on the surface, looks like a doll, with pale skin, voluminous red curls, and deep blue eyes. She is of average height and is slim and wiry from her outdoorsy and athletic disposition. However, her fierce temper quickly shatters the impression her appearance gives. Being an only child meant that Carmen is used to being the center of attention, and takes pride in outperforming others. She can be meddlesome, but is a fiercely loyal and just person, not afraid to speak out against perceived injustice or unfairness. Carmen always gives her all, mostly due to her competitive nature, and is reasonably talented at academics. Due to her constant energy, competition, and athletic ventures, Carmen has periods where she 'crashes' for a day or two, worn out and unmotivated, before diving back into her vivacious attitude and lifestyle. Bold, outgoing, and unafraid to tell it like it is, Carmen is a good friend to have and a nettlesome presence to those who dislike her.