Where are the bosses of the mini world? How to fight?

At present, there are three black dragon boss in the mini world, all of which are in the geocentric world and need to pass through the geocentric portal to reach them. As a boss, the black dragon is certainly more difficult to fight. When fighting, you must pay attention to avoid the attack of the black dragon. It's best to hide in the love center under the nest and avoid the flame from the black dragon.