If the X-axis symbolizes how far you can move in one universe, or the X-Space, and the Y-axis represents different universes, then the Z-axis is the intersection between the two former axes, the place where one can move between universes, otherwise known as Z-Space: The space that exists between the universes of the multiverse. Z-Space exists as a way to travel between different universes by travelling through the strange realm, and as a separate location itself. Debris that fall between the cracks of universes for any given reason tend to end up here, creating a strange ecosystem of minerals, creatures and technology from vastly different worlds, all scattered across impossible distances and twisting voids.
People that can travel between dimensions can freely access Z-Space, both heroes and villains using it as their headquarters or to move between other worlds. Of particular note, the villain Professor Zed and hero Justice are both known to have headquarters in different locations in Z-Space, even though their means of accessing the strange dimension differs greatly.
Strangely, Emerald Cities across the multiverse seem to have a connection to Z-Space.
Location and Appearance
Z-Space is located between universes in the multiverse, being the space that binds everything else together and allows travel between different realities, even if one does not have to pass through Z-Space to actually travel between realities. There's a number of ways to access Z-Space, and anything capable of travelling between different realities or dimensions can, in theory, access Z-Space. If a reality is destroyed or otherwise broken, such as during an incursion from Terminus, parts of the reality can end up in Z-Space, be it living creatures, buildings, technology, parts of worlds, or even entire worlds on their own. Z-Space itself is impossible vast, potentially endless, with the relative position of different bodies constantly changing, making finding anything close to impossible, at least unless you have some way of tracking them.
Appearance-wise, Z-Space at first glance appears much like outer space, but where normal space is dark with planets and stars, Z-Space is a swirling rainbow of random patterns and intermixing colors. Each color corresponds to a universe or dimension. Looking into the colors, one might catch glimpses of those other worlds. Stray bits of different realities float through Z-Space, ranging from singular buildings to entire worlds, chunks of rock, whatever one can imagine. They appear to move randomly through the colorful void, drifting through the great unreality that is Z-Space.
While Z-Space does not seem to have any oxygen or other breathable gasses, all that arrive in Z-Space appear perfectly capable of breathing.. Several beings have found themselves lost in Z-Space, living on the parts that have broken off from actual realities, surviving on whatever they can find. An unknown number of spaceships or other vessels capable of travelling through the chaotic void make their home in Z-Space, some on purpose, others simply being lost.
A number of heroes and villains that live in regular realities have crated homes and headquarters in Z-Space, which they can access through their own unique means, including the notorious Professor Zed and Justice Earth Prime.
As the space between universes in the Multiverse, Z-Space might not be reached by any dimensional traveller, but any dimensional traveller can potentially end up here, if they know how to reach it. On Earth Prime, Emerald City seems to have a special connection to Z-Space, with a few individuals reaching the rainbow void between worlds. Most notably, the dimensional raider Professor Zed was originally from Emerald City, but now resides at the floating fortress Zero Point within Z-Space. The 70'es heroine Miss Step could access Z-Space using her magic amulet, which she has since passed on to her granddaughter, Justice, who has furnished a structure in Z-Space as her headquarters, called the AnneX.
Whether through the actions of Professor Zed or by cosmic chance, beings and things that end up in Z-Space has been known to reach Emerald City, with both heroes and threats reaching Emerald City by traversing Z-Space.
Z-Space hold infinite power, its very nature defying the laws of physics and reality, which could, in theory, be harnessed for great and terrible things. While no such beings have yet to be confirmed to exist on Earth Prime, some believe that people that are naturally empowered by Z-Space exist, tapping into this vast power on their own.
In some ways, Z-Space stands in opposition to the Terminus. Where the Terminus is order and entropy, Z-Space is chaos and life. Where the Terminus is beyond the Omniverse, Z-Space stands within the multiverse. Somehow, it has remained undiscoverd by Omega.
Professor Zed: The dimensional raider Professor Zed, originally of Emerald City, Earth Prime, makes his home at the Zero Point fortress in Z-Space. From this flying fortress, he launches attacks across the multiverse, while he plans how to best make his triumphant return to Earth Prime.
Miss Step: A super hero from the 1970'es, who could access Z-Space using her magic amulet. She used these portals to store a great amount of equipment that she could retrieve to use to fight crime. Though she is long retired, some of her old equipment might still be found in Z-Space. She currently lives in Emerald City with her daughter and son-in-law, where she keeps an eye on her grandchildren, in particular one Robin Lynne Langley.
Justice: Emerald City native hero Justice came into the possession of Miss Step's magic amulet, a gift from her grandmother. Utilizing the amulet to access Z-Space to actually access Z-Space and make a headquarters there.
Drifters: A large number of creatures make their home in Z-Space. All manner of beings that have fallen through the cracks of realities to reach this place of unreality. One might all manner of things and beings, living and unliving, if one travels far enough in Z-Space. These drifters from the real world might be making their home in Z-Space, be bold explorers, or simply be lost. You never know what exactly you might encounter in Z-Space.
Z-Space has existed as long as the multiverse. A force of live and growth, it has somehow evaded the notice of Omega and the Terminus during their conquests across the Omniverse, standing as a sanctuary from the forces of the Terminus still.
In recent years, Z-Space's connection to Earth Prime has only strengthened, with first the incursions of Professor Zed, and later Justice's use of portals that access the rainbow void. How this will affect Z-Space and Earth Prime in the days to come are anyone's guess.