I always wanted a mountainous region in don't starve which got me thinking, it would be difficult to make a mountain biome but then I reminded myself of the caves and ruins. You could access the mountains on your world by repairing a rickety bridge (that spawns once randomly in the world at a border) for something like 8 planks and 4 rope. Once you cross it, it is similar to something like the caves where you go to a different world.
You enter in the start if the alpine region and it is permanently cold like winter and windy causing torches to be less effective. The entry biome is snowy and spawns berry bushes, twigs and trees. Animals could be a beefalo variant and other things (help me out here guys) basically similar to the ruins plains where it isnt too difficult to survive but has some stuff.
Hound variant: I thought of some kind of snow leopard that has much more health and damage but attacks in quick bursts and has to rest (can blend into the snow using fur). Drops monster meat, teeth or leopard fur that can craft new items.
Other biomes: Monastery: Similar to the city from the ruins in a way, stronger more dangerous mobs, new materials and crafting recipes, maybe a monk workshop station (similar to ancient pseudoscience station) I'm bad at coming up with mob ideas.
Ice lake: Would be the biome next to the first one, difficult to cross as you would be sliding everywhere and possible mobs could kill you like spiders or something. You can fish in the holes in the lake. During summer the ice lake melts leaving some chunks of ice and you can paddle across on that. Ice skates as a possible item to help you (Not sure how it would work as there is no foot slot, maybe a sled).
Other Features: Not sure about this but i think the boss of the region is obvious, yeti. Possible new resources; Iron, alpine flowers and other mountainous crop. Bears, more biomes. During winter the area is in permanent blizzard and dusk/night, would function similar to summer sandstorm. Antlion rage in summer causes avalanches (seems to fit really well). New item; winter gear, crafted with desert goggles, leopard fur and a hibernation vest. Takes up both body and hat slot but allows you to travel the mountains during winter. Possible mactusk civilisation?
Im open to any suggestions I think this idea is really cool and would love to hear what other people might add to it.