The urumashi are tall, ape-like people native to northern Ata. Their thick fur helps them survive north-Atan winters, while their upward-pointing tusks and powerful jaws tear through meat with ease. They also have one or two sets of horns on their head.

Many urumashi physical characteristics are determined by their childhood environment, not their ancestry. For example, urumashi that grow up on the ice plains develop thick white coats, while those that grow up in warmer climates develop thinner coats. Height, horn and teeth shape and size, and sensory acuity are also influenced by upbringing.

These differences form the basis of the three urumashi "greater tribes": the Ice Tribe, Cave Tribe, and Taiga Tribe. Each greater tribe comprises many smaller tribes, clans, or cities. Clans and cities generally speak a unique dialect of their greater tribe's language. These languages are in turn daughter languages of Uruman, which serves as the lingua franca of northern Ata.

Members of the Ice Tribe—or Tsimashi, in Uruman—have thick, white fur and dense underfur. They also have sharper teeth, longer horns, and larger builds than members of other greater tribes. Family tribes wander the ice plains nomadically, hunting seals and other game for their carnivorous diet. Their primary language is Tsi'ntai.

In a tradition called the Zad os LakiLaki Hunt, several family tribes will gather together to hunt whale-sized monsters called laki. This tradition occurs about once per decade across the entire Ice Plains. In weaker tribes, entire generations have never participated in a hunt. Despite the hunt's infrequency, many aspects of Tsimashi culture revolve around laki, which are seen as the epitome of nature.

While laki are feared and revered by the Tsimashi, worms are feared and despised. Normal worms aren't found on the ice, however; Tsimashi are only familiar with the deadly dab kuanabterrible worm. These massive marine worms dwell in icebergs that come from across the north. Tsimashi can identify north-sourced icebergs, and either avoid them or check them for dab kuanab. A worm attacks anything that approaches its host iceberg, even laki. It is thus imperative for Tsimashi to eliminate any dab kuanab they find, before the worm decimates local food populations.

Members of the Cave Tribe, or Khomashi, have dark, bristly fur and sensitive eyes. Both adaptations help them detect subterranean threats, the fur acting like whiskers to detect tremors in the ground. Their two sets of short, wide horns resemble armor. Their primary language is Kho'ntai.

Unlike the other greater tribes, the Khomashi are primarily farmers. The sun-facing slopes of the hills around their caves are well-tended, fertilized by bat guano. Deep in the caves, fungi thrive in volcanic seams. Most Khomashi live in shallow caverns between these farming zones.

Not much else is known about Khomashi, even by other urumashi. Kaitu'khttum are sent away young, and presumedly don't remember much of their home cities. Only a select few Zumashi traders are known to enter Khomashi cities; all other outsiders are generally prohibited. <redacted>

Members of the Taiga Tribe, or Zumashi, have hair-like fur in shades of brown, black, gray, orange, and even dark green. They also have a pungent odor, seemingly at odds with their keen smell. Their horns tend to curl like a ram's. Their primary language is Zu'ntai.

Zumashi trading clans, known as luamtraders to other greater tribes and outsiders, travel along seasonal trade routes. Other clans stay in permanent settlements, sometimes switching between winter and summer locations.

Typically, young urumashi develop the fur, teeth, and other traits of their greater tribe by age five. A small number of male children don't follow this pattern. Instead, their fur falls out, their horns grow erratically, and their bodies reach enormous sizes. Such boys are called Kaitu'khttum (or Kai for short), meaning "chosen by the power" (or "chosen"). Being "chosen" is both a blessing and a curse, for as much as the Kaitu'khttum are respected, they are feared more. They are exiled at a young age and go south, to the Atan Divide, where they join the ranks of their brethren-in-exile. There, the most brutish train to be warriors, while the more cunning are inducted into the religious order. Both soldiers and hierophants periodically patrol the urumashi lands to the north—or raid the human lands to the south.

The Kaitu'khttum weren't always considered "chosen". Long ago, the exiled boys were expected to perish alone. They were, after all, abnormally hungry children who wouldn't develop the necessary traits to survive anyways. That changed some centuries ago when a mysterious force began guiding the exiled children to the Divide. The Kai built a society of their own, their population growing entirely from the dismissed scraps of the greater tribes. They worshipped Khttum, or The Power, which guided them to the Divide. Once their numbers reached a critical mass, they emerged from secrecy and marched against the greater tribes. With surprise, physical might, and The Power at their back, the Kaitu'khttum crusaded across northern Ata and forcefully converted the other urumashi. All urumashi have ostensibly worshipped The Power since then, although pre-Power customs are still practiced in secret.

Most groups of humans have disproportionately high contact with the Kaitu'khttum compared to the greater tribes. Tanatenga and Sonnenland have both been raided by the Kai, and perceive the entire urumashi species as nothing but hulking savages with strange powers. Ogof also don't interact with the greater tribes, but since they live in caves, conflict with the Kaitu'khttum is rare. Shamalians are the only humans to have regular contact with any of the greater tribes.