import org.spongepowered.api.Sponge;
import org.spongepowered.api.data.DataContainer;
import org.spongepowered.api.world.biome.BiomeGenerationSettings;
import org.spongepowered.api.world.biome.BiomeType;
import org.spongepowered.api.world.gen.WorldGenerator;
import org.spongepowered.api.world.gen.WorldGeneratorModifier;
import org.spongepowered.api.world.storage.WorldProperties;

public class MyWorldGeneratorModifier implements WorldGeneratorModifier {

    @Override
    public String getId() {
        return "mypl:sample";
    }

    @Override
    public String getName() {
        return "Sample";
    }

    @Override
    public void modifyWorldGenerator(WorldProperties world, DataContainer settings, WorldGenerator worldGenerator) {
        for(BiomeType biome : Sponge.getRegistry().getAllOf(BiomeType.class)) {
            BiomeGenerationSettings biomeSettings = worldGenerator.getBiomeSettings(biome);
            // Как добавить сюда новый GroundCoverLayer?
        }
    }

}