Hello there, so I currently have this method that works, and my mob do spawn but it doesn't spawn them efficiently at all even though I have set the weight 100:

    @SubscribeEvent
    public static void onBiomeLoad(final BiomeLoadingEvent event)
    {
        if(event.getName() == null)
            return;
        MobSpawnSettingsBuilder spawns = event.getSpawns();
        if(event.getCategory().equals(Biome.BiomeCategory.SWAMP))
        {
            spawns.addSpawn(MobCategory.CREATURE, new MobSpawnSettings.SpawnerData(ModEntityTypes.CROAKER.get(), 100,2,4));
        }
    }

They basically spawn very rare, is there a better way or to fix this maybe?

one thing you can try is make your own category.

is your entity based on a vanilla hostile entity? probably not, but if it is, you need to override something that makes them despawn if they are too far.