So i thought that putting in this code allows my custom mob,a Troll to spawn naturally in biomes.

EntityRegistry.registerModEntity(EntityTroll.class,"Troll", 2, this , 40, 3, true);

EntityRegistry.addSpawn(EntityTroll.class, 10, 1, 1, EnumCreatureType.creature, BiomeGenBase.beach, BiomeGenBase.extremeHills, BiomeGenBase.extremeHillsEdge, BiomeGenBase.forest, BiomeGenBase.forestHills, BiomeGenBase.jungle, BiomeGenBase.jungleHills, BiomeGenBase.mushroomIsland, BiomeGenBase.mushroomIslandShore, BiomeGenBase.ocean, BiomeGenBase.plains, BiomeGenBase.river, BiomeGenBase.swampland);

I added this in my main mod file.

So far it doesnt spawn naturally and I'm only able to spawn it from eggs in Creative mode. Any suggestions or ideas as to where the code is wrong?

From my experience with  EnumCreatureType.creature I had to make the number a lot higher, like in the hundreds, however if you change it to EnumCreatureType.monster it should work with the lower numbers. Also inside your EntityTroll.class I would add this

 

@Override
protected boolean isValidLightLevel()
{
    return true; //lets it spawn during the day
}

 

This way it will spawn in any light level.

Hope that helps

Thanks a lot! Now I'm able to make them spawn naturally in the daylight without getting on fire