The setting is in tribal times.
I was thinking about a being (or a tribe of beings), living in arctic climates where the temperature is mostly or even exclusively below 0 °C, that is identical to an ordinary human with one important exception:
Their body is adapted to sub-zero temperatures and thus they can comfortably live and work without clothing (or with clothing only to cover their private parts) in sub-zero temperatures. This comes with a downside, though, since just as the bodies of ordinary humans have trouble in frosty temperatures and even run a risk of freezing to death, our "homo frostus" feels less and less comfortable as the air temperature raises and they even risk "melting to death" if exposed to warm temperatures severely enough.
The "obvious" conclusion is that such an adaptation would be extremely useful in arctic climates while confining such people to arctic climats only; but is this actually true?
Assume that "winter people" come to battle ordinary Eskimo. Both parties wear leather armors for protection. Now, however counter-intuitive this would be, the Eskimo seem to be at advantage: when a fighter exhaust himself, his body necessarily generates heat, which is captured by the leather clothing; as a result the Eskimo's requirement to maintain a high body temperature is met more easily, while the "winter people" have trouble in cooling their bodies and risk overheating. The "winter people" would solve this issue easily by forfeiting leather armors; but I suppose even if the armor is only made of hardened leather wearing such armor nevertheless provides a huge advantage during combat, basically dooming the unprotected to destruction.
Thus, being a "winter person" is actually a major disadvantage whenever things are going violent.
Is this analysis correct?
Background: Inspired by Ashe's story from LoL, I was thinking about a goddess of winter granting divine powers, including the said adaptation, to her few chosen ones. Such people would be great heroes, warriors and leaders, fabled through generations. Err... Thinking about it some more... Would they really? Wouldn't such a gift be more of a curse really, for reasons outlined above practically making such a person unable to defend themselves from anyone who does not enjoy the Goddess's powers?