First introduced to the Expanded Universe in Timothy Zahn’s Thrawn Trilogy through his arch villain Grand Admiral Thrawn, the Chiss have since developed into a popular species amongst fans and other Expanded Universe authors.

Homeworld

In the Expanded Universe, Csilla is identified as the homeworld of the Chiss. Csilla is a cold world of glaciers and snowy wastes located deep within Chiss Space, and serves as the capital of the Chiss Empire. Glaciers cover the normally warm equatorial regions of the planet, while solid ice locked the poles in perpetual winter. In order to survive, the Chiss had to build energy-efficient warrens beneath the ice, as close to the warmth of the inner planet as possible. Underground travel routes connect the various underground sections of Csilla. The iceways were bored through the bedrock of the planet, so that they were unaffected by the shifting ice found on the planet's surface. Specialized carriages moved passengers and cargo through the tunnels. Locked in ice for decades, Csilla has forced many socioeconomic and technological changes upon the Chiss, but few physical changes. Contrary to simplistic beliefs in a link between the Chiss skin color and the Csillan temperature, scientists have concluded that the Chiss’ blue skin is caused by a mineral found in the Csillan hydrosphere.

Csilla is also home to the Expeditionary Library, which is a huge, underground library that is maintained by the Chiss Expansionary Defense Force, and contains written information on virtually every planet, moon, and star system ever encountered by the Chiss. It is unusual, not because it is underneath the ice, but because every volume contained in the Library was hand-written.

Culture

Chiss culture is at the root of the disciplined species. Beyond their cold calculation, there are parts of Chiss culture that exhibit an intriguing mix of elegant beauty, which may be attributed to the differences caused in Chiss society after the glacial movement that plunged Csilla into its long ice age. Elements of the pre-glacial Chiss culture are visible in the smooth, striking lines of Chiss technology, as well as in Cheunh, the native tongue of the Chiss. Cheunh is a complex and creative language with an intricate syntax involving compound words made from a relatively small core of primary words, and the Chiss used detailed ideograms to represent concepts and combinations of images to represent complex ideas. A simple example of Cheunh can be seen in the three-part names used by the Chiss. For example, Grand Admiral Thrawn’s full name was Mitth'raw'nuruodo. The first component, Mitth, denotes a Chiss’ familial origins, but the second component, Raw is the center name, and Nuruodo serves as the house name. Upon entry into the Expansionary Defense Force, all Chiss soldiers are adopted into one of the ruling families during their time in service. The ruling families are known to adopt civilians as well in the fact that Thrawn's brother, Syndic Thrass, is also a part of Thrawn's ruling family with the full name Mitth'ras'safis. It should be noted that families and other close peers use a Chiss's core name which is formed using the last letter of the family name (or last two if they form a single sound like th) followed by the middle name and then ended with the first letter of the third name.