The Void was created by an incredibly old race who had lived to the end of their Universe's life. To escape the destruction of that Universe they created a new Universe, The Void. A Universe in which there was to be no perceived presence of time and infinite space available. It is unknown as to how old the Universe is exactly, but it is said to be an immortal universe, that existed before Continuum and will exist long after. How this was achieved is unknown.
It was not for many years before another race discovered The Void, it was both praised and feared when it was first discovered before many species learnt the benefits that it could grant them. Due to The Void having seemingly infinite size and no perceived time, it was used as both a prison and a refuge and is still used in this fashion to the present.
The Void is an Alternate Universe that spans for an infinite area. It is known as The Void because it contains very little of anything, there are no known structures or landmass of any kind. It is also interesting because there is no perceived presence of time, beings within The Void do not age.
One of the more interesting properties of The Void is its effect on those with super or preternatural powers, effectively, any being of these kinds within The Void is supposedly stripped of their powers and granted only the physical traits that exist naturally within that race. For instance, if a Human with the ability of Fire Manipulation were to exist in the void, they would no longer be able to create nor control fire at will.
The interesting conundrum pertaining to this property is races such as Xians, whose natural powers are considered to be supernatural. The ability to control other lifeforms and grant them a portion of the Xian's ability, this is more interesting when you consider the effect that The Void has on a being. The effects on a being such as the Xians are currently unconfirmed, however it has been commented that those that created The Void were similar, if not more powerful, than the Xian race. Another interesting properties of The Void is its unnatural physical effect to injury. Any body will recover sustained damage much faster than it would in it's home dimension, and even death is seemingly impossible within The Void. If one were to have the entirety of their atoms scattered across The Void, they would be revived to peak physical performance within a day, much is the same if a person were to theoretically bleed out in The Void. The time frame for healing is always considered, to the best knowledge of those experiencing it, to be 24 Earth Hours.
Access to The Void is granted by entering a Void Gate, a Void Gate is an Inter-Dimensional Portal that appears to exist within all known Universes. It appears seemingly without condition, transporting anything near the entrance in The Void to that Universe, and anything from that Universe to The Void. How this achieved is currently unknown, and why the Gate acts this way is also unknown.