Nightingale

Nightingale is an assassin and spy who gets hired by the wealthy to infiltrate and take out their opponents. She is considered to be one of the best assassin and spy out there with a 100% success rate in getting whatever the job done. 

From a young age, she was taken in by the Triad and was exposed to the world of assassins and spies. She was an orphan, lost, alone, and feeling vulnerable and when the Triad offered her  a means to survive she took it.

She grew up constantly undergoing vigorous training and even almost dying multiple times in the process. She became tough, determined, wise, and able to compartmentalise her emotions. 

She took the alias of Nightingale due to the fact she found them pretty and that there was a nightingale she would always see singing when she was little and living on the streets. This little bird gave her hope and made her forget the unbearable situation she was in.