Suggestion: Biosphere.

Redundant due to terraformer. Just use the Chilling TFBP or the Desertification TFBP or whatever.

I think its a cool idea. would be cool underground.... giant sphere (like biosphere generator mod) with controlable weather, climate, spawnrates, ect....

Yes, it would be a cool idea. Hey! Look! It already exists! It's called the terraformer, hayo.

@ above.

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Quote from legomaniack

@ above.

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all the important features (generating terrain of a specific biome) are included in terraformer. Having a device to control mob spawn rates would be grossly imba.

Last time i checked, all the teraformer could do that was related to a biosphere is:
A: Make snow
B: Plant trees
C:Burn trees, plant cactus.

This would be a controllable mini environment, with controllable:
Weather
Time (lighting)
terrain (including having hills mountains or flat)
hostiles on/off
Animals on/off
terraformer things listed above.