After-universe

The after-universe was the universe that existed after the destruction of N-Space, which in turn followed the pre-universe.

Prehistory
The Kotturuh believed they would continue to spread mortality, which they saw as a gift, in the universes after N-Space. (PROSE: The Dawn of the Kotturuh)

Intercepting the Eighth Doctor before he could take his TARDIS to the end of the universe, Straxus acknowledged that it could well mark the beginning of another, but that the new universe would not necessarily be any more hopeful than the last one. (AUDIO: The Great War)

The Tenth Doctor noted that if one was within a Void Ship, the end of the universe and the start of the next could pass them by. (TV: Army of Ghosts)

The City of the Saved was located between the previous universe and the next one. (PROSE: The Book of the War)

In one timeline of the N-Space universe where the Cybermen had gained dominance over time and space; at that universe's end, they intended to use the Eye of Harmony to shape the next universe's formation so it would be a reality perfectly suited to them. They were stopped by the Twelfth Doctor and Rassilon retroactively erasing the Cybermen's dominion over N-Space. (COMIC: Supremacy of the Cybermen)

Properties
According to one account, it contained twenty-seven dimensions, including underspace, and was a pink void inhabited by green mists of orbiting plankton, (PROSE: Millennial Rites) while another account described it as a deep-green void containing green planets, green stars, yellow mist and a green, electrical-looking energy. (COMIC: The Stockbridge Child)

Inhabitants
The Zytragupten were one species known to inhabit this universe, (COMIC: The Stockbridge Child) and Saraquazel was also native to this universe. There were also mindless grazers which had eyeclusters, void-drifters which had (or travelled inside) triple helices, and fuction-breeders which nested in artificial constructs. This universe was connected to N-Space through pan-dimensional vacuum emboitments. (PROSE: Millennial Rites)

Another account claimed the entire universe was a hive intelligence called the Myriad, which attacked N-Space in the 12th century in an attempt to hasten their existence, the Myriad Army playing "The March of the Myriad" as they attacked planets. (AUDIO: The Lure of the Nomad)