The Chelgrians, described in Look to Windward, are a recently contacted race, which subsequently suffered a major civil war with billions of dead when a failed Culture intervention caused a collapse of its millennia-old caste system.
The Chelgrians are a mammalian species with two sexes, male and female, and evolved from an apex predator of their homeworld. They somewhat resemble a tiger with six legs. However, in the course of evolving from animal to sentient being the mid legs have fused, making them tripedal (walking on the rear legs and the mid leg). They are between three and four metres in length and one and a half to two metres in height, and have two arms ending in six digit hands that resemble paws. They are furred with various markings and have large carnivore teeth.
The Culture had decided to change Chelgrian society via covert intervention to diminish the caste system that was considered an impediment to Chel’s development. Unfortunately Chel erupted into civil war as an indirect result of the Culture’s actions. Shocked by this disastrous turn of events, the Culture announced that they had been manipulating Chel all along. The admission succeeded in stopping the war, but also created strong hatred towards the Culture.
The need of the Chelgrien-Puen (the sublimed part of the Chelgrian society) to take revenge on the Culture drives the events in Look to Windward.
Chelgrian society takes the form of a rigidly enforced caste system, though sufficiently technologically advanced to be considered Involved (that is to say similarly advanced to the majority of space faring species).
They are an especially notable race because of an event in their history, as six percent of the Chelgrian population sublimed when they had been Involved for only a few hundred years. For this to happen to a young race is unusual, for it to happen to only part of a race more so, and there was another unexpected and remarkable outcome: the sublimed part of the population maintained links with the majority part of the population which has not moved on, calling itself the Chelgrian-Puen (the 'gone before'). As a unique phenomenon in the Culture universe, it also strongly influences the society's outlook, as the Chelgrian-Puen consider themselves (and are accepted as) the gatekeepers of the Chelgrian heaven.