The Void

The Void was what the Time Lords called the emptiness found between all parallel universes, different dimensions, and other realities. It was known to the Eternals as "'the Howling" and to others as "Hell"; (TV: Army of Ghosts) it was also called the "Great Space-Time Void" (GAME: The First Adventure) or "dimensional interface", (AUDIO: The Eternal Summer) and was compared to a kind of limbo by Sutekh (COMIC: Old Girl) and the Third Doctor. (TV: Inferno)

The Void was often used as a place of banishment for destructive or dangerous beings exiled from their home universes. These included, at various times, beings native to N-Space like an army of Daleks (TV: Doomsday) and the Osiran deity Sutekh, (COMIC: Old Girl) and beings from "outside" the universe, such as Sunyata, (PROSE: Night of the Intelligence) the Cybermen of a parallel world, (TV: Doomsday, The Next Doctor) the King Nocturne, the Dragon and one of the Gods of Ragnarok. (COMIC: Old Girl)

Nature
The Void contained no light or darkness. It also featured no temporal or spatial dimensions (neither "up" nor "down"), but the Tenth Doctor used some spatial language to conceptualise how the Void was "in between" all the universes which were "stacked up against each other". Even time in most senses did not actually exist there. Anyone who entered the Void could choose to let eternity pass them by: they would "exist outside the whole of creation" and would be completely unaffected by events as major as the end of their home universe or the start of another. (TV: Army of Ghosts)

A Void Ship was a spaceship which could enter, traverse, and exit the Void into other dimensions due to being constructed so as not to really exist within its original reality. Even the Time Lords, (TV: Army of Ghosts) whose TARDISes were nevertheless occasionally capable of traversing dimensions, (TV: Rise of the Cybermen) believed such a vessel to be a theoretical concept only, impossible to build in their reality, though they were proven wrong by the Cult of Skaro during the Last Great Time War. (TV: Army of Ghosts) All material which travelled through the Void absorbed a particular type of harmless background radiation, which the Doctor called Void stuff. The longer a material had been present within the Void, the more "Void stuff" it became saturated with. (TV: Doomsday)

Native life
The Tenth Doctor asserted that no life existed naturally inside the Void. (TV: Army of Ghosts) However, the Twelfth Doctor discovered that the Fractures were beings that lived inside the Void, and compared them to antibodies for the multiverse. (COMIC: The Fractures)

Chronomites naturally traversed space-time "riptides" and the Void. (GAME: TARDIS)

According to ancient Gallifreyan myth, the Mi'en Kalarash inhabited "the wasteland between realities". (AUDIO: House of Blue Fire) The Terrordactyls were native to the "Great Space-Time Void". (GAME: The First Adventure)

Ancient history
One of Rassilon's titles was "Ravager of the Void". (AUDIO: Neverland) According to one account, Sunyata resided in the Void, and manifested inside the universe as various avatars of the Great Intelligence. (PROSE: Night of the Intelligence)

Under the Time Lords
While the Time Lords ruled N-Space, it was relatively easy for them and their agents to cross between dimensions. (TV: Rise of the Cybermen)

When crossing from his world to that of the "Inferno Earth", the Third Doctor briefly experienced passing through what he described as "a sort of limbo". (TV: Inferno) The Fifth Doctor and Nyssa became trapped in the "dimensional interface," the "space between worlds" after escaping a collapsing time bubble, but later broke free. (AUDIO: The Eternal Summer)

After being trapped by the Fourth Doctor in a reprogrammed time corridor meant to age him to death, Sutekh made use of an escape hatch to which he had earlier availed himself, "stepping sideways" into the Void. He was trapped there with countless other gods originating from other realities. Some had come there of their own accord to wait out eternities, but others were trapped. Of those, many, such as one of the Gods of Ragnarok, had previously tried to take N-Space but been foiled by the Doctor; they thirsted for revenge and tried to bargain with Sutekh. They knew that, being native to N-Space, he would one day be able to return there, and begged him to help them cross over as well when he did, promising him their allegiance. (COMIC: Old Girl)

When the Eleventh Doctor was, for a time, erased from existence by stepping into the cracks, River Song described him as being condemned to the never-space, the Void between worlds. (TV: The Big Bang)

During the Time War
Pessimistic about the outcome of the Last Great Time War, the Cult of Skaro decided to ensure the Dalek race's survival by escaping into the Void using the Sphere, a Void Ship of their own design, and waiting out the rest of the War from its confines. Within it, they carried the Genesis Ark, a prison ship they had stolen from the Time Lords, which contained millions of trapped Daleks. (TV: Doomsday)

Consequences of the War
The Ninth Doctor jettisoned the Matryoshka drive powering Hesguard Institute into the Void, in order to put a stop to the use, and subsequent uprising, of Sin-Eaters on criminals. (COMIC: Sin-Eaters)

In 2007, to his dismay, the Tenth Doctor identified the object around which Torchwood Tower had been constructed as a Void Ship, and explained its significance to the befuddled human scientists. Soon it was discovered that this mysterious bronze sphere was the Cult of Skaro's Void Ship, with the Cult exiting it triumphantly.

As it returned to the universe, the Cult's Void Ship created a breach between N-Space and an adjacent parallel universe, causing them to "collide" into each other. (TV: Army of Ghosts) Falling through this gap in the Space-Time Vortex, the Doctor's TARDIS was able to crash-land in the parallel universe, which the Doctor would later label Pete's World. (TV: Rise of the Cybermen)

Some time later, Pete's World's Cybermen took notice of the "wake" of the Daleks' sphere and used it to cross over to N-Space, hoping to convert its human population on top of that of their own world. (TV: Army of Ghosts)

As the Dalek force, freed from the Genesis Ark, began to exterminate the Cybermen army in the Battle of Canary Wharf, the Tenth Doctor widened only one side of the Void breach. Since they were saturated in Void stuff, all of the Cybermen and all but 4 of the Daleks were sucked back into it. The breach then permanently sealed itself. (TV: Doomsday) The four Daleks of the Cult of Skaro escaped being hurled into the Void by means of an emergency temporal shift to Manhattan in 1930. (TV: Daleks in Manhattan)

In 2008, Cybermen survivors of the Battle of Canary Wharf who hadn't been sucked into the Void as they were cyber-converted during the battle attempted to force the Doctor to reopen the Void and release the Cybermen trapped inside. The Doctor insisted that he was unable to do so, leading to a Cybermen attack on a military base. However, the military repelled the attack, killing most of the Cybermen who kidnapped Martha Jones and held her hostage at the Millennium Dome to force the Doctor's compliance. The Doctor feigned compliance, but in actuality opened a space-time portal to the Jurassic era rather than a portal to the Void. A T-rex that came through the portal briefly destroyed two of the remaining Cybermen while the Doctor destroyed their leader, foiling the plot. (PROSE: Made of Steel)

Trapped in the Void, the Pete's World Cybermen stole or scavenged two things from the Daleks who were trapped with them: intelligence about the Doctor, and a Dimension Vault. Although the Doctor believed that the tests of the New Dalek Empire's reality bomb caused all living things within the Void to die, he discovered some of the Pete's World Cybermen back in N-Space; he theorised that they had been ejected from the Void beforehand through some sort of rift. They were able to use the Dimension Vault to travel to 1851 London, where they built a CyberKing. (TV: The Next Doctor)

Gods and monsters in the Void
A memory changing alien known as Adam Smith, who faced off with Torchwood Three, claimed to have escaped from the Void. (TV: Adam)

Sutekh, still trapped in the Void, was joined in his banishment by the King Nocturne, (COMIC: Old Girl) a conceptual entity whose quantum make-up the Tenth Doctor had managed to destabilise, (COMIC: The Jazz Monster) as well as by the Destroyer, (COMIC: Old Girl) a demon whose physical form had been destroyed by Alistair Gordon Lethbridge-Stewart in Arthur's World. (TV: Battlefield)

Eventually, Anubekh, a splinter of Sutekh's consciousness whom he had left inside the Hand of Sutekh in case he should be banished from the world, awoke and possessed Sutekh's son Anubis. Anubekh was able to take control of the Circle of Transcendence and release Sutekh, and several of the gods with whom he had allied himself, from the Void. Sutekh sought to prevent the Doctor from sucking him back into the Void by "plugging" the Circle of Transcendence with the Destroyer, but was, before long, forced back into the Void by his own Hand of Sutekh, who had, unbeknownst to him, merged with the consciousness of the selfless human Dorothy Bell. In the process, Bell herself became trapped in the Void, sacrificing her freedom to prevent the Doctor from making this same sacrifice in her place. (COMIC: Old Girl)

When the Eleventh Doctor was, for a time, erased from existence by stepping into the cracks, River Song described him as being condemned to the never-space, the Void between worlds. (TV: The Big Bang)

Behind the scenes

 * Before making use of "the Void" in his script for TV: Army of Ghosts, Russell T Davies had mentioned an Ultimate Void, located "beyond the Time Vortex", as one of the battlefields of the War in PROSE: Meet the Doctor. Although it is more likely than not that he loosely intended for the two Voids to be one and the same, no valid source has ever confirmed the link.
 * Although metaphysically questionable, the concept of a Void Between Worlds is far from being unique to Doctor Who, instead being a staple of science-fiction and fantasy works involving a multiverse or omniverse, as is the idea of various horrors being exiled there and trying to make their way back into "our" world.

Le Void