Cotd

Commonly referred to as Strangers by other groups.
A formerly nomadic people who discovered small pinpricks of dimensional bleed through to Darkness. They came to revere it, performing rituals that widened the tears and weakened the boundaries.
Around a century later, those people settled in the area, now molded by the darkness that they brought forth. They have famous unnaturally pale skin, and hair so black that it (actually does, in fact) darkens its surroundings. Their eyes have adapted to see Darklight , like natives to the plane, while still being able to perceive ordinary light. Like most things that live in the dark, their lifespans extended indefinitely, free from the typical decline of age.
Outsiders that have managed to visit tend to be terrified by what they see (and don't see), but the civilization is not inherently evil. Just because their horses' skin and muscle are only perceptible in darklight does not mean one should run screaming from people riding faintly glowing skeletons.
As a general rule, the people themselves are not fans of conquering the outside. With no known way to introduce darkness to new areas quickly without causing the dimensional equivalent of severe radiation poisoning, the rate of expansion is limited.
Most that venture outside of the forest are rather discomforted by the lack of darklight, resulting in merchants from the region being famously irritable. A group have formed settlements in the vast unclaimed lands in the north, one of the few other places that feel like home.

Abilities

The race's people all have a high natural affinity to darkness. While the Midlanders gained theirs through the specific ritual of consuming salamanders, adaptation to darkness came as a natural consequence to simply existing in the area.
A strange quirk of Cotd biology is the fact that their eyesight deteriorates if fingers and toes are cut off. The exact mechanism is unknown, but it's thought that these appendages may be 'anchors' for the extradimensional magic which allows their eyes to filter out darklight.
Cotd are generally highly resistant to visual transmission vectors of magic for two reasons. First is their secondary darklight vision, which reduces the strength/focus of 'normal' vision. Second is the umbrite which naturally forms from accumulated darklight within the eye. Consequently, it's rather hard to damage a Cotd's eyes in general- scratched corneas really aren't a thing. This also significantly slows pupil dilation speed, making adjusting between light levels far slower.

Appearance

Taller than average.
Cotd natural light coloration is paler than most, as if there were a washed out filter over it. This doesn't come up much since they don't have the reserves to practice arcanism, but it shows in their eye colors.
Very pale skin, almost bleached white in appearance. Skin tone variation takes the form of translucency of skin/muscle layers, with extreme cases having bones visible through almost cloudy-glass-like skin and muscles. Hair and nails (keratin, really) emit darklight, therefore showing up as pitch black and soaking in light. They're tougher than ordinary keratin structures, essentially being naturally occurring umbrite.

Soul & Appearance

Though Cotd often look picturesque and ethereal in a physical sense, their souls are a different story. At best grotesque, Cotd souls are mangled messes stitched together to accommodate their modifications, getting worse every generation (hence the requirement for increasing amounts of soul energy in childbirth).
These two facts are actually intrinsically tied together. Internal Observer Effect (Celestial flubbing) affects development of the baby during pregnancy. Naturally, mothers tend to want their children to be beautiful. Because Cotd spend so much soul energy in their modifications, this dramatically amplifies the impact of flubbing to the point that every baby is affected by it (whereas in most cultures, only extremely powerful individuals even have minor impacts on their children's appearance through sheer Celestial flubbing, and only Titan-level entities are guaranteed this level of influence). This comes at the intrinsic cost of the children having dramatically reduced soul reserves, so it's not all good. This also does mean that rather monstruous entities can be birthed in certain circumstances where the child is thought of with revulsion (i.e. rape, mental disorders etc.).
Cotd tend to have very samey faces due to this. It's a bit of a self-perpetuating cycle: as everyone approaches the same ideal, people have a harder time picturing attractive features any other way. Chasm dwellers don't run into this anywhere near as much due to their increased contact with other cultures.

Eyes

Darklight vision isn't quite like standard vision- it doesn't just cut out past the field of view so much as it progressively gets murkier. While focused around the eyes, it's possible to somewhat infer the surroundings outside of one's standard field of view, vaguely like echolocation heavily skewed towards the front of the person. It's not intuitive to consciously acknowledge, requiring some practice. Those more used to ordinary vision get subconscious hints from it at most, while the more learned can effectively see slightly around corners. Those with white eyes are almost guaranteed to be able to do this, completely lacking normal vision to create inhibitive preconceptions.
Important to note is that white-eyed Cotd aren't blind in that they have no capacity for vision: they just naturally have a filter over their eyes which completely blocks out visible light. It'd be theoretically possible to surgically remove these in order to allow light to shine through, though it's actually more feasible to simply transplant an eye from another person.
3 main eye colors:
-white: Can only see darklight. Eye is more reflective-transparent than white upon closer inspection due to the tissue being extremely adapted towards darklight (and reflecting all visible light while being mostly phased out of the world). Occurs more in insular groups far from the border, along with being a common symptom of inbreeding.
-black: Can see darklight and ordinary light. most common eye color.
-red: Can only see ordinary light for the most part, 'legally' (but not utterly) blind to darklight. Common occurrence in first generation children of mixed race parents (after which the non darklight-perceiving eyes tend to completely win out).

White comes from a near-purely Darkness-based organ, which therefore has practically no effect on the visible spectrum. Black comes from a fully mixed organ, as the darkness affinity captures darklight, while having to interact with ordinary light makes it 'exist'. Red comes from the darkness affinity not fully capturing, and instead diffusing the blood color.
Eye color can be on a spectrum, going white -(gray)> black -(dark red)> red.