Tian Xia is the continent that lies directly across the globe from the original location of the World Weep.
Tian Xia was the continent least affected by the opening of the Weep. Generally, Mathesis's alchemical wrath was reserved for the sides of the world she could see. As a result, only the Hero's March (and its losses incurred) affected Tian Xia significantly. Unrest, unease, and disaster in Tian Xia was generally caused by either the environmental effects of the Weep or the nations of Tian Xia themselves—not the Alchemist's direct actions.