The Kig-Yar are a dinosaur-like saurian species. Following their assimilation in 1342 CE, the Kig-Yar served the Covenant until its dissolution in 2552. Many went on to aid its remnants as mercenaries, privateers, and pirates, though the majority stayed independent of any such factions.
Kig-Yar share many features with Earth avians as well as reptiles and exhibit several features that are common among species that have evolved in low-gravity environments, such as Lacerta erectus. Their legs are sinewy and muscular, and are digitigrade in structure like those of birds. Though they have been mistaken for carnivores, the Kig-Yar are apparently an omnivorous species. Kig-Yar possess very sharp teeth, and their jaws are tipped with a hooked, bird-like beak. Both their hands and feet are tridactyl, and are armed with sharp talons. Their hands, in particular, exhibit an unusual structure, with a single large middle finger surrounded by two opposable thumbs. Their eyes are protected by a nictitating membrane that sweeps across the eyes horizontally. Starved Kig-Yar have been known to eat the flesh of fallen enemies, as well as that of live prisoners. They are gifted with extraordinarily acute senses of sight, hearing, and smell, making them adept as scouts and snipers in the Covenant military. Kig-Yar are also very agile and can execute swift jumps and rolls in combat; these abilities are most pronounced in the more muscular T'vaoan subspecies, members of which can leap great distances and cover ground at extremely high speeds. Kig-Yar possess a strong salty, occasionally acrid stench.
Young Kig-Yar chicks are covered in a brown fledgling down, which gradually molts and gives way to scales and plumage as they age. Male Kig-Yar possess plumes of spiny quills at the back of the head and on the elbows; the color of this plumage indicates the Kig-Yar's mood. Quill color also varies between subspecies; Jackal quills typically have brown, red, or light blue coloration, whereas T'vaoans generally have black or reddish feathers. Ruuhtian females lack these quills, instead having calloused plates at the forearms and the rear of the head. This thick skin helps protect the female during courtship: when mating, the male will often bite, chew, and tear at the back of the female's head, neck, and arms. Apart from these differences as well as those in reproductive organs, there is no meaningful physical variance between male and female Kig-Yar.
While Kig-Yar are somewhat physically frail, they are capable of moving quickly to evade harm. Their blood is bright purple in color, similar to that of the Sangheili, possibly showing a similar chemical makeup. They lack high amounts of calcium in their skeletons, which makes them a poor source of biomass for the Flood. Thus, Kig-Yar that are infected by the Flood are typically turned directly into carrier forms rather than combat forms. However, they have been utilized as combat forms during at least one engagement, the Battle of Trove.
To humans, Kig-Yar are known to have a distinctly salty and occasionally acrid smell about them. Kig-Yar occasionally suffered parasitism from feather mites, tapeworms, and fleas. They also suffered from a microbial affliction known as jha-sig, commonly caused by unhygienic food.