Elva is an orphaned baby who, in the first book of the Inheritance Cycle, Eragon attempts to bless, but accidentally curses. (Eragon intends to say 'May you be shielded from misfortune', but accidentally says 'May you be a shield from misfortune'.) As a result, Elva is compelled to protect other people from misfortune at the cost of her own peace of mind. Due to the curse, Elva has to increase her size to better protect those around her. At the end of "Brisingr" she is less than two years old, but her body is said to be at the development of around six years old, whereas her mind develops adult faculties. Her abilities develop until she is able to anticipate events in detail two to three hours in advance. However, she struggles before fights, due to the amount of pain and suffering about to take place. She has been taken on as Nasuada's bodyguard.
In Brisingr, Elva continues to advise Nasuada. This, and Elva's loyalty to the Varden, are terminated when Eragon, attempting to remove the spell he placed on her, instead modifies it to the extent that although she is aware of others' suffering, she is able to ignore it without pain to herself. He also unintentionally allows Elva to turn off her conscience, which she uses against him. She remains with the Varden, under the care of Angela, who has rendered herself immune to Elva's powers by a spell.
Read more about this topic: List Of Inheritance Cycle Characters, Characters Associated With The Varden