The Parallel Universe is a universe where all the logic is twisted. Often times, substances from this universe have different properties but are used the same way as they are in the regular universe.
In this universe, rather than having the three dimensions composed of an x-axis, a y-axis, and a z-axis, the three dimensions are instead composed of an x-axis, a y-axis, and an ℳ-axis. These axes are used to traverse the Parallel Universe.
In order to travel between the regular universe and the Parallel Universe, one will either need to use technology that allows to warp across the z-axis or the ℳ-axis depending on the universe one is currently in or be lucky enough to find a wormhole that rips apart the fabric of the z-axis and ℳ-axis in order to cross to the other side. However, to create such technology is both expensive and time-consuing, and wormholes rarely last more than a few minutes in any environment before collapsing in on itself.
Those that cross universes can choose to stay in the other universe, but their physical self will eventually try to revert itself back by replacing the third dimension coordinate of the opposite universe to the third dimension coordinate of their current universe. This causes increasing instability which may result in twisting of all the coordinates. While it is not noticeable when in the opposite universe, when the physical form eventually gets out of the opposite third coordinate and into their original third coordinate, they risk teleporting to a random location as according to the twisted coordinates.
The Parallel Universe is also much more chaotic than the regular universe. Color cycling is present in most of the substances, and most liquids act like they're boiling all of the time despite their temperatures being roughly equivalent to their corresponding substance in the regular universe.
This universe is also suffering from an uprising of Corruption, spreading extremely quickly after taking over a large, flying being. The entirety of this universe is at risk of being uninhabitable, which brings problems along for those who inhabit the Parallel Universe.