In terms of anatomy, the Tseetsk appear remarkably similar to certain of Earth’s flightless birds. Doctor Crusher theorized that the Tseetsk may have started out as shore-dwelling, swimming birds. The Tseetsk are a dimorphic race. An average female Tseetsk outwardly and comically resembles a chicken about the size of a ten-year-old child, with soft down in hues of yellow and green, and had flipper-like wings that ended in slender clawed hands. Males are noted to be bigger, at least twice the size, and with beaks more wedge shaped.
An unique trait that the Tseetsk possess is a pheromonal defense mechanism called the stink. When threatened, a Tseetsk can produce a scent that can attack the sensory input centers of the victim's brain.
Tseetsk civilization goes back over ten thousand years, forming the political interstellar nation called the Sphere of Clans. Originally the Tseetsk were divided into separate clans namely: the Sree-Tseetsk, the Joost-Tseetsk, the Loor-Tseetsk, and the Kraaxaa-Tseetsk. About 10,432 years ago, war broke out amongst the various clans due their obsession with their specialized forms.
During the war, the Loor and the Kraaxaa were allied against the Sree and the Joost. In the end the Sree-Tseetsk were all that was left of their mighty great race.
Over the next millennia the Sree steadily began to rebuild their civilization, slowly reclaiming the world they lost. To avoid another war, the Sree adopted a policy to ensure their species survival, forbidding any violence upon each other. They manipulated their historical records and inputted several cultural taboos on various sciences and philosophies to erase their war-like history and self-immolation.
Their policy worked for a time, their homeworld being a prime example of a utopia where hunger and poverty was non-existent. However in 2190 on the world Foothold, the Sree made first contact with an alien species: Humanity. At the time the Sree had yet to make contact with any civilized culture in their sector of space. The humans as they learned from them were refugees from the Eugenics War, who sought sanctuary in the depths of space to establish a new colony. The humans of Foothold were survivors of a crash-landing and nearly facing death. In addition the Sree faced a philosophical problem as they were unable to see humans as equals and their war-like ways proved to be disturbing. The Sree dominated an incorporated them into a slave caste to serve as labors in re-terraforming the Sphere of Clans lost holdings.
The humans were spread out across the sector to rebuild the Tseetsk holdings. In 2390, the USS Enterprise came about to Koorne, and made contact with the lost humans, its arrival and the free humans aboard prompt a slave rebellion against the human overseers and Tseetsk regent, Draagh. However the overseers managed to send a tachyon signal to the homeworld.
The human slaves led by Korban attempted to convince the Enterprise to wage a war upon the Tseetsk. However Picard and former overseer Vossted opted for a diplomatic solution. Dissatisfied with a peaceful solution, Korban had Picard and Troi kidnapped and held hostage to force the Enterprise's cooperation. Two Tseetsk ships arrived and when faced with the Enterprise prepared to destroy them.
Picard and Troi were led to a secure area in the mountains, however they and their captors were attacked by savage ice creatures, who were later on revealed to be regressed Kraaxaa-Tseetsk. The Kraaxaa held the two Starfleet officers on account for the human slaves actions for murdering several of their tribesmen, orders directed from the Sree to pacify all hostile lifeforms in the effort of re-terraforming Koorne.
The surviving clan of Tseetsk were later revealed to the Sree commander and the horrible revelation that they ordered the murders of their own people through the humans and called off the attack. A week later, the Federation sent Ambassador Struthio to mediate the disputes among the three parties. (TNG novel: Chains of Command)
It is unknown what the original Tseetsk culture was like before its fragmentation. Only two offshoots of the Tseetsk remain: the Sree-Tseetsk and the Kraaxaa-Tseetsk. However after the cataclysm that claimed their world, both cultures have a relatively narrow view of the universe and other races. The various clans each spoke a distinct dialect of Tseetsk.
The Sree-Tseetsk are the current mantle-holders and forebears of current Tseetsk society. The race is strictly hierarchical, and strongly matriarchal, having females in position of power while the males serve as breeders. After the genocidal war the Sree-Tseetsk emerged from it with a single objective: to keep the race from dying out.
Unlike their Sree-Tseetsk cousins, this offshoot have somewhat regressed into a tribal culture. Though major differences being that the Kraaxaa have lost none of their history and maintain a patriarchal society. They retain enough technical expertise to maintain their geothermal heat tap, thanks to a supercomputer maintain by their priesthood.
The main branch of Tseetsk, the Sree-Tseetsk retain almost all aspects of their technology from the golden age of their civilization. Their medicine is said to be extraordinary. They’ve eradicated every one of their major diseases, including those as trivial as their equivalent of the common cold. Yet some subjects, like genetics, are absolutely taboo. The same goes for cosmology and nuclear physics — they want no part of any science that deals with the fundamental structure of things, due to their narrow-view of the universe no doubt.
According to Data the Tseetsk are way ahead of the Federation in cybernetics technology as well as shipbuilding. Tseetsk ship are estimated to be five to seven times the size of a Galaxy-class starship.