The Xi'an are a spacefaring civilization that originated on the planet RyiXy'an (Hyoton III). They are capable of space flight, quantum travel, jump point navigation, and planetary terraformation. Their leader, Emperor Kr.ē, has reigned over the Xi'an Empire (SaoXy'an) since SEY 2643 (MXY III.926).
Humans first made contact with the Xi'an in the Xi'an-controlled Th.us'ūng system in SEY 2530 (MXY III.838), when Human-owned Gaia Planet Services attempted to start terraforming operations on Th.us'ūng III, having done so without approval from the government and without having surveyed the planet to learn that it was already inhabited. After first contact, the Xi'an and Human governments entered into a period of sustained conflict known as the Xi'an-Human Cold War.
Military buildup on both sides resulted in the creation of the Perry Line in SEY 2542 (MXY III.847) as a buffer between the two factions. At its height, the Perry Line consisted of eight planetary systems with jump points connecting Xi'an and Human territories. At the end of the Cold War, the Perry Line systems were demilitarized, divided, and annexed into the United Empire of Earth (UEE) and the Xi'an Empire. The end of the Cold War has brought warmer relations between the two governments.