In the second trilogy of the series, there is the 4th book which is called Blood Brothers, then Shadow Sister and finally Bronze Bird Tower.

This is a story of a young slave girl who believes she is not worthy of a name but finds within herself the strength and courage to make this perilous journey, and do what must be done.

In the far western mountains of the Han Empire in ancient China, a young slave girl is used, abused and neglected by the cruel Master Lan, whose job is to care for the two aged imperial dragons, Long Danzi and Lu Yu.

Danzi and Ping travel via the Yellow River to Wucheng, a town of sorcerers, to recover the stone.

However, before she can respond, their boat collides with an imperial yacht, and Ping and Danzi are taken into custody at the Emperor's hunting lodge.

At the peak, Ping realizes that Wang Cao and Danzi are also on Tai Shang, with Diao attacking them.

Produced by Manuel Cristobal, Larry Levene, Huang Jun, Gabriel Arias-Salgado, Axel Kuschevatzky, Mikel Lejarza and Mercedes Gamero, the film is directed by Ignacio Ferreras and co-directed by Zhang Bo with the screenplay written by Ferreras, Carole Wilkinson, Rosanna Cecchini, Pablo Castrillo and Xiamping Wang.