Neo Bowser Castle

Neo Bowser Castle is a large, black, ominous castle that is a mix of Bowser and Antasma's designs located above the skies, until it is grounded and then located in the east, north of Somnom Woods and east of Mount Pajamaja. It can be reached by traveling north in the area between Mushrise Park and Somnom Woods.

History
At the summit of Mount Pajamaja, with the Dream Stone charged, Antasma wishes for a castle for him and Bowser, one that is impenetrable and also one that is feared. A large castle, a mix between Bowser's and Antasma's designs, comes out of the Dream Stone and floats into the sky. Antasma then tries out the castle and destroys several small islands around Pi'illo Island with large lasers. Then a large impenetrable shield surrounds the castle. Bowser dubs this castle Neo Bowser Castle. Inaccessible for most of the game, Mario and Luigi gather the parts of the Ultibed to reach the Zeekeeper in the dream world, as he is the one who can break the shield surrounding Neo Bowser Castle and send it to the ground so the brothers can defeat Antasma and Bowser.

Areas

 * Area 1: Mario and Luigi enter the castle itself in this area, with a shop just outside the entrance. Switches that lower gates are present, with one gate blocking entry to the first dream world, where Kamek is fought.
 * Area 2: A very expansive second floor, it is divided in two sections. Mega Bob-ombs are used to press the gates' switches. There are two dream world spots where the Bros. must go to defeat Kamek. On the first floor's foyer, two Warp Pipes are present which can transport the Bros.: the one on the left leads to the beginning of the floor; the pipe on the right leads to the end, near the elevator that leads to the third floor.
 * Area 3: Three giant flames from the dream worlds blocking entry to the fourth area are present; the Bros. must make their way to the three dream worlds from the west and east sides to make them disappear. Several outdoor areas are here as well.
 * Area 4: The final area of Neo Bowser Castle.
 * Bowser's Bedroom: This room is where Bowser sleeps to provide power to the castle. The gigantic Dream Vines beneath Bowser's bed serve as a Dreampoint, to the seventh and final dream world. At the end of this room is an elevator that leads the brothers outside.
 * Main Lair: This outside area is where Antasma is fought for the final time. At the end of this room is the entrance of the castle's tallest tower.
 * Spiral Staircase: A long, spiral rainbow-colored passageway Mario and Luigi must work their way up to reach elevator that goes to the balcony. The former Elite Trio is there to throw Bob-Ombs and Mega Bob-ombs at them to slow them down.
 * Balcony: The final floor where the final battle with Dreamy Bowser is fought.