Yetifur is in the pit in Weezer Forest, one north of the bottom. Beware, as there are ice yetis and bears in the forest.
This mutation grants:
+ cold resistance +1 brawn +1-2 beat resistance immunity to environmental cold +brains, +brawn when in cold areas yetis will not attack you
Yetifur gives you complete immunity to environmental cold which can be useful in the few cold areas there are in the game. Your passive temperature will never fall below 10c. It also gives buffs to brawn and brains when in cold areas, which can be useful for crafters, as you can just craft in your freezer for the +brains. In a freezer, you get +3 brawn, +2 brains. You also get +1 brawn and +1-2 beat resistance which speaks for itself. Ice yetis and normal yetis will not aggro you. Stench and chiller become more effective when taken in conjunction with this (needs testing!).
Your body temperature will be increased by ~10°C, which can be very annoying in warm areas and requires micromanagement.
Dishdashas/Keffiyehs/HEV suit, drinking lots of water or being covered in antifreeze vomit helps with that.
S/He is covered in shaggy white fur.