This is so sad. They just die instantly. Please fix this. I suggest a mob spawning dimension blacklist.

    @Override
	public boolean getCanSpawnHere() {
		if(this.dimension == DimensionType.OVERWORLD.getId())
			return super.getCanSpawnHere();
		else return false;
	}

Hmm, I think I only missed setting up Raven's condition. Most other mobs were already restricted to spawn in the overworld dimension with the code above.

Dimension allow list will be added in the next update.