Yi-Hlenga

Size

They’re muscular types, despite being medium height, matching humans. Of the Hlenga, they have the most muscle mass, with matching control over muscle which allows them to manipulate their size and girth to hide to show their flaps when needed. They can also use it as a form of shock absorption and, historically, as a means to ward off enemies and a mating call.

Flight

They have large flaps between their limbs, which give them the ability to catch the wind, lifting them, to glide for long enough to match flying.

They are, in reality, extremely flexible, able to twist and contort their bodies into most shapes. This matched with a great natural awareness that allows them to very soundly spin directly into branches and leaves to avoid being cut up or breaking bones.

Their muscle mass and flexibility combined with sharp nails allow them to be expert climbers.

Their climbing ability with gliding makes them borderline unstoppable able to completely outrun multiple races within the forestry of the Black Thorne.

This makes their hunting ability on par with few, making them powerful but culturally responsible as they could logically wipe out a population of a creature. But also allows them to domesticate groups of creatures most others would never imagine.

Altitude Sickness

The Yi have a very strong inbuilt immunity to high altitudes able to live in the highest of clouds safely even if they have never lived in high altitudes, meaning the City Yi and the country Yi.

Fighting

They have a raised sense of aggression, at least towards each other. They are extremely violent, often without anger. This is not culture, but both a mental and biological trait untamed through the centuries.

The sense of violence and aggression is vital for their growth as they need to fight and grapple against each other, beating on each other as a form of play, encouraged by their parents.

The means of fighting will almost entirely consist of grappling, more specifically wrestling, entire traditions and cultures wrapped around the sport, their gods being strong backers of the sports.

The biological purpose being to master their muscles so completely they can develop their ability to glide at their highest speeds and bunch their bodies upwards or in any direction needed.

Without such their natural ability could be greatly hindered, sometimes to the point of not being able to climb at all.

Civilization and Culture

Beauty Ideals

Muscle plays a very large part of beauty within the eyes of both Yi men and women.
This is still considered to be a means for finding a sexual partner. Historically the males and females would themselves to show off their size, fight very much like wild animals to express good genes and dominance.
Deformities are hard to spot amongst on Yi but to them it’s clear as day.