Yhetis are a type of monster that live in high mountain peaks all over the world, far above altitudes that most animal species, including humans, can comfortably survive in. This has resulted in extreme adaptation to cold weather. While most people would assume that the yheti is merely a feral, over-adapted mammal, this is incorrect. The yheti is actually an elemental beast; it doesn't need to protect itself against the cold because ice is its core element.
Because of this, a yheti's body temperature is actually much COLDER than that of the areas where they tend to live, and it allows them to blow gusts of freezing ice to defend themselves. The yheti's thick coat of hair, which most people assume is for insulation, is mostly to provide extra traction in a snow-slick environment and protect their bodies from wind-blown hail. Yhetis live in small, nuclear families rather than tribes or packs, and inside their territory usually consider all creatures outside of their immediate family to be either food or a nuisance. Outside in relative civilization, they tend to be lazy and easy-going, but woe betide the one who angers a yheti.
Unlike, say, a hellhound, whose temper is sudden and explosive, a yheti's temper is more like a blizzard, slow to build but nearly unstoppable once unleashed. Possessed of super strength, magical frost breath and a body so numb with cold that they can barely feel pain, the yheti is difficult to put down once enraged.