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now i get it. Tank you so much you have really made my day

Only of it is something specific that the default vanilla features can't solve. For ore generation you could use Feature.ORE (default ore generation), Feature.EMERALD_ORE (which generates only in mountain biome) or Feature.No_SURFACE_ORE (ancient debris feature, an ore that has no contact with air blocks)

Not easily. And older save formats don't support an increased world height either. (In fact, I'm pretty sure the current save format goes back to like 1.7. Edit: just checked, Anvil has been in use since 1.2.1)

You would need to listen to BiomeLoadingEvent (), you could register an function to it like this: MinecraftForge.EVENT_BUS.addListener(EventPriority.HIGH, onBiomeLoading); As from the javadocs of the event: "This event fires when a Biome is created from json or when a registered biome is re-created for worldgen" With this done you would just need to "treat" the biome in the listener and add any feature (like ore generation) you need. An exemple of listener: public static void onBiomeLoading(final BiomeLoadingEvent event) { /* Check which biome are being loaded, example: if the biome is TAIGA or SWAMP */ if (event.getCategory() == Biome.Category.TAIGA || event.getCategory() == Biome.Category.SWAMP) { /* Get UNDERGROUND_ORES features of the biome */ event.getGeneration().getFeatures(GenerationStage.Decoration.UNDERGROUND_ORES ).add( /* adding COAL_ORE with some configuration */ () -> Blocks.COAL_ORE.withConfiguration(...) ); } } As from the configuration you could look at the Vanilla default ore generation features to get what you want.