C.C. is immortal, healing from any kind of wound, (even fatal injuries with enough time.) And not aging either. C.C. also has the ability to bestow people with Geass, a power that manifests differently in each person but usually the ability to affect the minds of those it is used on in some way. (Mostly by eye contact) A Geass sigil appears on her forehead whenever she uses this power has a similar scar on her left breast. Her powers caught the interest of Britannia who imprisoned her for experimentation purposes.
Unintentionally C.C. triggers a trap set by V.V., causing herself and Lelouch to be submerged in a shock image sequence similar to the one she used on Suzaku. Through this, Lelouch sees memories of her past, including repeated "deaths" from times as a nurse attempting to escape from a World War I-esque battlefield, only to be shot in the forehead to later showing her being persecuted as a witch and suffering various forms of torture and/or execution throughout history, including burning at the stake, guillotining, and the iron maiden, a minimum lifespan of at least five centuries could be determined. In the past she appears to have observed Suzaku and Lelouch when they were both children having actually interacted with Lelouch at one point even if he doesn't remember their meeting.
Her individual experiences have led C.C. to become a detached and lonely individual, with little care for even those she has entered into contracts with and even tells Lelouch that she has been alive so long that she can no longer remember who loves her and who hates her, because of her nature and history she has been lonely as long as she can remember.
Yet would eventually get an obsessive taste for pizza, and be fascinated by Cheese-kun and several related items, she constantly orders pizzas to Lelouch's house using his credit card. (This is often used for comedic effect.) Her love for pizza is so strong that she is willing to risk herself being captured, twice nearly exposing herself to get a piece of a giant pizza being made by the Student Council (which is ruined both times); both Lelouch and Kallen sometimes refer her as "Pizza Girl". at times she is often seen hugging a Cheese-kun plush doll.
