The cessyre (plural - cessyres) is a strange breed of feline found commonly in many of the temperate, sub-tropical, and tropical zones of Sidereus. Originally indigenous only to the eastern areas of Catherna, the creatures were often domesticated by Chatûl hunters and rangers, who coveted the creatures as pets due to their considerable combat prowess. Eventually the art of domesticating cessyre became known to Jade Elven pirates who began to capture the creatures for breeding and sale. By the middle of the Third Age, the popularity of cessyres had dwindled somewhat because they proved difficult to tame by any who were not of Chatûl or Elven ancestry. Thanks to the short period of prolific breeding and trade, they can now be found in many places around the globe.

The cessyre loosely resembles a panther or other great cat, with clusters of large semi-translucent whiskers at its face, shoulders, elbows, and hips. The most notable features of the cessyre are its long and lanky body shape - which includes a disproportionately long neck - and the creature's seemingly oversized head. Cessyre have strange features, as they are able to bear all of their teeth with relative ease, leading many who witness them to believe the animal is "grinning". Adding to this effect, a phosphorescent substance in the creature's hair, eyes, teeth and bones cause its teeth to glow in the right light. Since the cessyre is largely nocturnal - this means they are often seen as a pair of eyes and a distorted "grin" bobbing in the darkness. A typical cessyre has a silvery-grey coat with black, blue or purple stripes (though in the case of blue or purple stripes the coloring is so dark as to be nearly impossible to distinguish from black). Females range in length from 5 to 6 feet, and weigh 350 pounds; males are 6 to 8 feet long, and weigh up to 400 pounds. Their eyes glow bright violet or blue, even after death.

The cessyre is a savage creature and a fierce fighter that is quick to defend itself if it feels threatened. In the wild, it is highly aggressive in its home territory. If another creature enters the cessyre's domain it will attack without hesitation. The phosphorescent chemical in the cessyre's body allows it to generate a bright pulse of bio-luminescence. This pulse can occasionally cause hallucinations, and frequently at least disorients those it fights - making the cessyre a formidable opponent. Cessyres are pack animals, gathering in groups called a "cackle" or a "congregation". Cessyres are carnivores, often females will do the hunting for the pack, though males will periodically join in the hunt as well - seemingly for enjoyment. Cessyres have been known to develop a "taste" for humanoid meat. When this happens, a congregation of cessyres can become very dangerous very quickly as they can be voracious eaters and enjoy harassing their prey before bringing them down. A cessyre congregation does everything in a group - including the raising of young. On occasion, a hunting party may become smaller due to a large number of expectant or nursing mothers - or a particularly weak congregation. Rogue cessyres split from a congregation of their own will often strike out alone or in very small hunting groups. These rogues are often males who are not strong enough to take control of their own congregation.

For reasons that remain a mystery, cessyre have a very ordered and almost choreographed way of fighting amongst themselves for leadership. These conflicts are almost always non-lethal and resemble a dance in many ways. The battles will almost always be only to first blood, with the defeated cessyre leaving the area - shamed. Cessyres mate aggressively in the winter, with a gestation period of roughly nine weeks. As a result many of their young are born in the spring. The cubs, about the size of small dogs, reach maturity, though not full size, within 4 months. They remain in the with the congregation until their about a year of age. At this point, males are often ejected from the congregation to find a new group, and females remain. While raising young, the congregation is fiercely protective of its lair. Some adults always remain with the cubs, while the others go off to hunt. Dead prey is dragged back to the lair to be eaten by the congregation - expectant mothers and young always eat first, followed by the males. Lairs are littered with the bones, equipment, and the treasures of the prey.

Cessyres have little to fear from other large predators, save trolls - who seem to enjoy cessyre meat in their stew. Some wizards and alchemists value their hides for use in certain magical preparations, and will offer generous rewards for them. The eyes, teeth and fur of a cessyre are a highly prized component for both magical and alchemical purposes.