Void Tower

The Void Tower is a supposedly hidden area in the Fourth Floor of Princess Peach's Castle. Unlike the Lunar Tower or Solar Tower, it is not commonly accessed by following a staircase. Instead, many report that completing every other present instance of a Celestial Tower and its respective levels makes a ray of light appear in the main hall of the Fourth Floor, which acts a teleporter to the Void Tower.

The Void Tower features a unique soundtrack, which can be listened to here.

Appearance
The area's structure is reported to be yet again identical to the Lunar Tower and the Solar Tower, being very tall, shaped like an octagon, and it's floor being covered with grass and concrete. The roof of the tower is shaped like a cone and shares textures with the castle's roof. It is currently not known what level can be accessed by looking at the ceiling of the tower, however it will depict a black hole before the level has been beaten, and change to an image of a identically shaped cloud after. The skybox in this area also switches from depicting a black hole on the horizon of a purple sky to a cloudy, blue sky after beating the level in question. This mirrors features of the other Celestial Towers, along with the rumored level accessed through the ceiling of the Void Tower becoming inaccessible after it has been completed. Attempting to leave the Void Tower after having entered it is only possible by passing through a dark hole in the wall, where other Celestial Towers would have a door. Although it is not entirely clear where this leads the player to, reports mention destinations like the Castle Courtyard, Flower Fields, World of Opposites or the World of Dreams, while a few other players report the game to just crash. These inconsistencies, together with the verified fact that the destination can even be a course or area that is usually not part of the respective copy, have lead to theories about the Void Tower's nature and purpose, with varying degrees of evidence for them. While some believe that the Void Tower supposedly possesses the ability to connect the player to a copy of a different, apparently random person around the world, the most accepted, yet still heavily debated, theory states that the destinations are "just" heavily personalized on the spot with the only purpose of acting as a place the player can be transported to, as the destination of the hole in the Void Tower is supposedly not defined. What speaks against this theory however, is the apparently perceived consistency within the inconsistencies, meaning players have reported feeling like the place they have been transported to, to be in some way related to either what they had done before entering the Void Tower, or in some instances even before they had started the game. As mentioned before, the tower apparently contains a way to access an as of yet unknown course by looking directly at the black hole on the ceiling of the tower, which is supposedly dependent on the Internal Weather System, as the course can only be accessed during a rare event in which Peach's Castle and all areas around it become filled with fog. Before beating the related course, the fog is also reported to be unusually strong, heavily obscuring the player's view while the wind pushes them around. After the course in question has been completed however, the black hole has turned into a cloud and the fog becomes as usual.

Eternal Null statue
The area also contains a unique statue similar to the Eternal Star, however the stand is empty. The text on the plaque is reported to remain blank until the tower's respective level has been beaten. The text will then simply read "NULL", which is why this statue is referred to as such. This aspect is strangely consistent considering its simple nature. A theory proposes a connection to a theorized file integral to the AI's functionality referred to as "NULL.avi", which is also believed to be part of the full Oman Archive, though this has not yet been verified nor proven.