Intimidating beings, Chiss were near-humans, meaning their shape, features, and dimensions were greatly similar to those of humans. However, some notable differences were that their skin was blue, their hair a shimmering blue-black, their eyes a glowing red, and they had angular faces. Because of those first two characteristics, they were mistaken for Pantorans, blue-skinned humanoids from Pantora, although Pantorans did not have red eyes. Besides their coloration, Chiss eyes were slightly better than those of humans, their visible spectrum going into the infrared range. Additionally, their hearing was sharper and their reflexes were faster.

Force-sensitivity, referred to as the Sight by the Chiss, was incredibly rare and manifested in limited abilities, namely precognition, which was Third Sight, and telepathy, which was known as Second Sight. Force-sensitive Chiss were almost always female. As they grew older, their abilities diminished and eventually disappeared. The secrets of Second and Third Sights were among the best-kept secrets in the Chiss Ascendancy, to such an extent that many Chiss were unaware of their full extent or even their existence. While he was familiar with the intricacies of Third Sight, Chiss Imperial Grand Admiral Mitth’raw’nuruodo knew of the existence of Second Sight but was unaware of its abilities. Young females identified with the ability to use the Sight were trained to act as navigators for the Chiss fleet through the treacherous hyperspace routes of the Unknown Regions. They were known as ozyly-esehembo, the Cheunh word for “sky-walker.”

The ruling class of the Chiss Ascendancy was known as the Aristocra. The supreme legislative and executive body of the Ascendancy was the Chiss Syndicure. The Chiss military consisted of the Chiss Defense Force and the Chiss Expansionary Defense Fleet.

The Chiss were renowned throughout the Unknown Regions for their military might as well as their perceived just military doctrine. Even among species with no direct contact with the Chiss Ascendancy, stories and legends of the Chiss as blue-skinned noble warriors flourished. This was true even among species that had apparently performed no space travel for decades. During a devastating civil war on her homeworld, a leader named the Magys fled with 200 refugees to the Rapacc system, where they settled. The Magys’ refugees warned the native Paccosh of invaders who would seek to destroy the Paccosh people, and encouraged them to dispatch refugees to preserve their culture. She told her hosts legends of the Chiss as noble warriors famously capable of disabling their enemies without destroying them, leading the Paccosh to send a refugee ship to the Dioya system at the edge of Chiss space in the hopes of seeking Chiss aid. Uingali foar Marocsaa later tested the identity of Senior Captain Thrawn by challenging him to disable a Paccosh freighter without destroying it.

The primary Chiss language was Cheunh, though in their rare contacts with outsiders, the Chiss used trade languages such as Sy Bisti, Meese Caulf, Taarja, and Minnisiat. Written communication was done in the Cheunh script. Those who disliked Chiss used the derogatory nickname “blueskin” for them.

Most Chiss names were polysyllabic and consisted of three parts, as in Mitth’raw’nuruodo. The first portion identified an individual’s family, the second was the given name, and the third indicated other social factors. Aside from the long form of their names, the Chiss also used shortened variants—for example, “Mitth’raw’nuruodo” could be shortened to “Thrawn.” These short form names were known as core names, and for the sake of expediency, core names were conventionally used in all except the most formal situations. In a rare case of an outsider among the Chiss, the human Eli Vanto was given the standard three-part name “Eli’van’to,” which his shipmates reduced to the core name “Ivant.”

Chiss were omnivorous and ate foods such as cheese, yubal, and plant products.