If Silk Fox, not Dawn Star, is put in charge of guarding Kang the Mad and the bridge at Dirge she will be spoken to by a spirit. Instead of heading left down the stairs to the bridge, head right down the stairs. The chest is invisible and is sitting behind the fountain. Walk near it and it will appear.
The story of the Broken Bough is a sad page in the history of the Jade Empire. When Emperor Zuwan, ninth emperor in the time of divisions, died suddenly with no heir, his wife, Seng Si, assumed the throne to prevent chaos. Though respected, she was seen as merely a ceremonial caretaker. When war erupted a decade later the Imperial Army would not follow her orders, so she took up a sword and asked instead that they follow her lead. Emperors lead armies only in legends; Seng Si's commitment stunned her detractors, and her death shamed the nation. Seng Si the Broken Bough changed the face of the Imperial court, though the relics of her rule were never displayed.
Silk Fox's weapon can harm spirits.