Nightingale was born into the Ashford family. Her mother died shortly after she was born and she was primarily raised by her father, though she also spent much time with her loving grandfather. While growing up, Gale learned all about her family history and about the Guardian Spirits from her grandfather, in particular the family's long quest in recollecting all the missing Keys. The Ashford family long ago made a contract in blood with the Guardian Spirits in which both parties were bound to protect each other for all eternity. This also meant that only members of the Ashford family could use their keys. Other mages to grew jealous of their power and raided the Ashford family home, stealing many of the keys and greatly weakening the Ashford family.
Every year on her birthday, Gale's grandfather would give her a Guardian Spirit Key while also teaching her Guardian Spirit Magic. When her grandfather passed away, she swore that she would find all the Keys to honor his memory and restore her family's legacy. However, her father heavily protested against this due to his fear that Gale would end up like her mother: dying while trying to find all the Keys. He even went so far as confiscating her Keys in an attempt to dissuade her from becoming a Guardian Spirit Mage.
Despite this, Gale left her father, taking all her belongings in her magical bag. She eventually came across and joined the Titan Wing Guild, partaking in jobs with her partner Verick Houston, whom she met upon joining the Guild, while also searching for the Keys. She already possesses all the Keys recovered so far as well as a few that she has found on her own. Of them all, she primarily uses the Keys of Azreal, Huginn and Muninn, Beowulf, Ahool, and Chimera.