The Multiverse.
A dimension in which all universes reside. The multiverse is made up of a limitless number of bubbles. Each bubble represents a different universe that can either be very similar or vastly different from its surrounding neighbors. All manner of universes reside within the multiverse.
To peak in one an observer might see a world in which the asteroid that killed the dinosaurs never hit the earth and the dinosaurs were never killed off. In that world mammals never evolved to become the dominant species on the planet. In that world humans never existed. In another universe fish never left the ocean and all manner of life evolved to live under the water, including a species similar to humans, but with fish tails instead of legs. This species formed a complicated and lasting society that still prospers in their universe to this day.
Sometimes worlds are very similar, except for one or two significant differences. Two such universes, which coincidently, happened to be floating near each other, were perfect examples. Each had similar histories until one fateful event.
In both universes a group of humans with extra ordinary abilities began to emerge. Some of the humans stood on the side of justice, while others stood only for themselves. Because of the super powered advantage each universe had, both strived for and achieved reaching the stars. But for one universe evil was about to take hold.
In both universes there was a wicked and vile man whose intentions were to create a machine to get rid of all the so-called superheroes. In one universe, Universe 616, the heroes banded together and were able to stop the villain from seeing his plan to fruition. In the other universe, Universe 3692, the heroes failed, the villain created his machine and set it off, but with unexpected consequences.
The machine not only stripped the heroes of their abilities, but also stripped the villains. All super-powered people were affected. Furthermore, the machine affected the genetics of all humans so that no super powered person would ever be born again.
Life continued on in Universe 3692 and several years after the incident the Galactic Federation was conceived to counter the alien threats and the human element thrived.
In Universe 616 the super powered individuals, both hero and villain, continued to prosper.
But both universes were on a collision course with each other.
While it was next to impossible to cross the dimensional gap between universes, every so often it happened…