BiomeTweakerCore uses ASM to enable several features in BiomeTweaker:
- Enabling vanilla generation to recognize more than stone as a filler block (addActualFillerBlocks command).
- Overriding top and filler blocks in more "stubborn" biomes.
- Setting the oceanic top and filler blocks (set command).
- Setting the grass, foliage, and sky color of biomes (set command).
- Setting the waterColor in more "stubborn" biomes.
You can configure BiomeTweakerCore to enable only the features you want it to. By default, it enables none.
You can find BiomeTweaker here:
https://minecraft.curseforge.com/projects/biometweaker
Please note: BiomeTweaker will work fine without BiomeTweakerCore. It simply enables the features listed above. Only use BiomeTweakerCore with BiomeTweaker 3.0+.