The Xi'An are a long lived (several hundred years) reptilian-looking humanoid species which developed an expansive interestellar civilisation which occupies at least fourteen systems in the Milky Way galaxy. While not inherently aggressive or expansionist in their nature, the Xi'An history is rife with civil war and power struggles with the result that all X'ians, military or civilian, are apt fighters. However, they prefer subtlety and manipulation to overt conflict.
Their political system is based on hereditary monarchy. The emperor has a High Council of Advisers, each representing a facet of the government. Each colony emulate this structure with every planetary council member reporting to their respective counterparts on the Emperor's Council.
The Xi'An Empire had first contact with humans in 2530 and this encounter immediately escalated into a 259 year cold war (2530-2789).
Source: Star Citizen Upcoming game by Chris Roberts and Roberts Space Industries.
Note: This species has been announced as being part of the upcoming Star Citizen game universe. More informations will become available when the game comes out.