Audentia was originally a Time Lord. Her first incarnation was killed in the Time War by Daleks, and her second incarnation was forced to turn herself into human and forget everything about her home planet and species. After 8 human years, Audentia is now 17 years old. She ran into a mysterious woman named River Song, who told her she was a Time Lord. With a hand-me-down Vortex Manipulator and a Sonic Cellphone, she's seeking adventure in her life and friends to face dangers with. And it's basically suicide since she never thought of reverting herself back to Time Lord.
Audentia is Latin for courage, which I think is suitable for my character.