The imaginary universe, also known as the realm of imagination, is where the majority of Problem Sleuth, and apparently Jailbreak and Bard Quest, take place. The imaginary universe consists of the Imaginary City Streets and the four kingdoms sandwiched on top of one another, with the Cathedral of Syndetic Ascension adjoining the two. Gravity pulls objects towards whichever half of the imaginary universe they are closest to, creating a gravity plane directly in the center. It is also home to the horrific beasts.
Characters can access the imaginary universe by either playing make-believe in a fort, which causes them to manifest in the imaginary universe in an imaginary body, or by physically entering it through a window. Windows are also the only way for inanimate objects to pass between the real world and the imaginary one. If one's imaginary self passes through a window, they find themselves unable to maintain their imaginary form in the real world, and . Characters with high imagination stats can use special abilities such as creating objects, transforming themselves, and duplicating themselves while in the imaginary universe. Extraordinarily high imagination allows characters playing make-believe to act in the real and imaginary worlds simultaneously using a battle technique called Abstracted Thought.
The imaginary universe is much, much wider than it is tall. Though the Four Heroes managed to scale the entire Cathedral of Syndetic Ascension on foot in a short amount of time, it takes energy traveling at the speed of light billions of years to travel along the perpendicular fan cord.
Due to an oversight on the part of the creator, Dark Matter Mobster Kingpin was for a time several million times more massive than the imaginary universe.
The universe temporarily shrank due to the effects of Black Hole Mobster Kingpin's gravitational pull, pulling everything to its singularity. The Cathedral of Syndetic Ascension also started to telescope due to the effects from this. The imaginary universe was reverted to normal when the black hole was destroyed.