4Game

I think a cool addition to the game would be rare biomes within biomes that contain unique items. Below a few examples. I think biomes in general lack a bit of variation and reason to go back once you have beaten them. It could be more rewarding to explore, not to find absolutely necessary items but to find nice to have items that increase the quality of living.

Biome: swamp
Sub biome: raised bog
Characteristics: surrounded by regular swamp, let's in sunlight. Inhabits a carnivorous plant that attacks when in its vicinity – item drop could be poison glands used to charge any melee weapon. Other drops could be peat used as compost to enhance the soil quality of cultivated land for faster growing crops.

Biome: meadow
Sub biome: river
Characteristics: flowing water with unique fish species. Contains willow trees that can be cut down and used to make passive fish traps – catch could include trout or crayfish that unlock unique recipes.

Biome: mountain
Sub biome: glacier
Characteristics: semi icy and slippery environment that can be hollowed out anywhere with a pickaxe. Will contain one ancient weapon/ armor that can be repaired but not upgraded.

There should be more incentive to explore anywhere at any stage of the game!