Volgon8

New to java-ish here so don't shoot me please but: Would it be because your AC_BiomeGenBase is not considered a BiomeGenBase for when it is called from AC_ChunkProvider's biomesForGeneration field on line 92? Which in turn calls AC_WorldChunkManager and returns the array of AC_BiomeGenBase(line 227) containing your two biomes FrostForest and FrostMountains where they are trying to be converted to a BiomeGenBase. Probably a noob question but why couldn't you just add some biomes and set them not to spawn like BiomeGenHell(unless if you are in the nether of course). I'm not too familiar with creating a new biome, but I like messing around with world gen a bit too much.