The road to the final battle
To accomplish this mission, you must first catch Shadow Mario once in all worlds, i.e. you must mine in all worlds. Complete mission 7. Once you have done this, the entire city is flooded and Shadow Mario appears on Shine Gate. Now walk on the rooftops of the city to the left side of Shine Gate and climb the way up. There you will see a cave that is now open and leads you to Corona Mountain.
Corona Mountain
When you’re in the volcano, you have to jump from platform to platform to reach Bowser. But beware, because at regular intervals, nails appear on the platforms. Some platforms, but are impassable by fire, here you should use the FLUDD and suffocate the flames for a short time. There is no real trick here, be quick and take care that you are not hurt by the nails. If there is not enough time and you get the flames on the next platform extinguished, you have to jump up and keep yourself in the air over the nail platform with the Hover Nozzle as long as possible. But once the platform field is overcome, the next task awaits you. Because now you have to cross the lava lake, you have a wooden boat at your disposal. But first charge the FLUDD with water (using the water jet that is there). You can control the boat if you push yourself from behind with the FLUDD. Turn off the obstacles (rocks) to the large platform at the very end. This is the last task before the final fight against Bowser. Grab the Rocket Nozzle and shoot yourself up on the cloud. Magnify it a little by spraying it with water and change the camera view so that you have a plan view. Now shoot yourself a little bit higher until you finally arrive at the top of Bowser.
The fight against Bowser
After a short cutscene, the fight begins. Unlike usual, you do not attack Bowser directly, but have to slowly destroy his swimming pool. Go to the outer ends where there is a flame symbol and shoot yourself into the air with the Rocket Nozzle. At the highest point you use a ground pound. This breaks off this end. Quickly get to the edge of Bowser’s pool and find the next spot. FLUDD always tells you how many more you need to destroy. Be careful not to be hit by a Bullet Bill in between. You can destroy them either by jumping or by water. Bowser's fire breath is just as dangerous, but it can also be eliminated with water. If all five ends are destroyed, the pool breaks apart and you have won the fight.
Corona Mountain Blue Coins
The final ten Blue Coins share the same collection guide as Delfino Plaza and the Airstrip. Use the Corona Mountain section to collect the coins over the lava and along the boat route.