Three years after the war against the Sky People, the Metkayina clan seeks to establish a vital trade alliance with the Tsawke’ite, a mysterious Na'vi clan dwelling above the sunless deep-sea trenches. Eager to prove his readiness as a future leader, Ao’nung joins the diplomatic voyage to the Sinking Shelves. There, he meets Siofra, a serene and sharp-witted deep-sea artisan whose ethereal appearance and effortless command over the dangerous, open-ocean currents completely upend his expectations.