Council of Eight's universe

The Council of Eight's universe, known by them as History, was a version of N-Space without free will which was created and maintained by the Council of Eight from the universe's own endpoint at the Vortex Palace. This created a paradoxical situation in which the Council fought to maintain the events which led to creation of themselves and their Palace.

The reality initially existed as one of many possibilities in the post-War universe, but after the multiverse collapse it was the only universe in existence for some time. With the primary purpose of this reality being to protect the Council, much of its alterations to history were attempts to weaken the Doctor. (PROSE: Sometime Never...)

Creation
The Council were already creating their own reality before the events which led to their existence, using hourglasses in the Vortex Palace which bonded to an individual's timeline and crystallized a desired version of it into a part of the Council's History. The Council began targeting rival potential temporal lords of the post-War universe, (PROSE: Sometime Never...) such as the Vortex Wraiths, (PROSE: The Slow Empire) Clock People, (PROSE: Anachrophobia) and the Oracle.(PROSE: The Domino Effect) When attempting to control the Eighth Doctor using an hourglass, the Council found that his anarchic nature meant that his timeline ended up controlling the hourglass rather than the other way around, with the process putting great pressure on the Doctor's second heart until it was stolen by Sabbath Dei.

The Doctor's free will in the face of History's crystallization led to him becoming the Council's biggest threat. The Council could still use their hourglasses on his companions, so they began to weaken the Doctor's timeline by killing them. However, the Doctor could still counter these attempts; (PROSE: Sometime Never...) the Seventh Doctor learned of Ace's crystalized death in advance (PROSE: Prime Time) and was then able to "save" Ace by replacing her with a near-identical parallel universe equivalent immediately following her death. (PROSE: Loving the Alien) Being unable to redo a crystalized event, the Council realized that the multiverse was a threat to their total control of existence. (PROSE: Sometime Never...)

The multiverse was also a threat to the Council because it meant that any one reality was only one of "hundreds, thousands, millions upon millions" overlapping and intermingling quantum possibilities. (PROSE: Wolfsbane,Time Zero) Therefore, to stabilize their fragile universe into an unopposed History, the Council instructed Sabbath to manipulate the Doctor into initiating the multiverse collapse. (PROSE: Sometime Never...) The Doctor eventually was able to end the multiverse collapse by establishing one universe as the only reality in existence. This act created the Council of Eight and destroyed all quantum free will except the Doctor's. (PROSE: Timeless)

Existence
The universe was created in a Big Bang which was witnessed by the time travellers Chloe, Erasmus, and Jamais. As a result of interference from several temporal factions, Chloe possessed a doll with Guy Adams' DNA which contained sleeping sentient diamonds that got caught in the big bang and were awoken. (PROSE: Timeless) As the universe grew, fragments of the diamonds were spread all across it, communicating with each other and observing the entire timeline. When, many millennia later, the Big Crunch approached, the diamonds were all crunched back together and became the Council of Eight. From the end of the universe, the Council were able to manipulate everything which had came before into their own web of time. Sabbath Dei and the Time Agency were among the Council's operatives in the past used to maintain History. (PROSE: Sometime Never...)

In this universe, many of the Doctor's companions were given premature deaths, including Harry Sullivan, (PROSE: Sometime Never..., Wolfsbane) Melanie Bush, (PROSE: Sometime Never..., Heritage) Ace, (PROSE: Sometime Never..., Prime Time, Heritage, Loving the Alien) and Sarah Jane Smith. (PROSE: Sometime Never..., Bullet Time) Others, such as Jo Jones, were removed from history entirely by being placed in Schrödinger Cells. Additionally, Sam Jones had the alterations to her timeline undone, so that she died of a drug overdose in her early twenties. (PROSE: Sometime Never...)

End of dominance
When the Vortex Palace and all its hourglasses were destroyed, this universe's supremacy over reality was destroyed and the multiverse was restored. While the Doctor saw the Council dying, the nature of the multiverse meant that their reality still existed somewhere. Many of the Council's harmful alterations to companions' timelines were undone, (PROSE: Sometime Never...) although Sam Jones remained the version of herself who died of an overdose at a young age. (PROSE: The Gallifrey Chronicles)

When experiencing multiple timelines of her life, Melanie Bush had memories of the timeline where she died on Heritage. (AUDIO: He Jests at Scars...)