Non-world

Non-worlds were locations or areas of reality which had a causal relationship to the Spiral Politic, but no physical existence in the conventional universe. As such, they were a source of great annoyance to the Great Houses during the War in Heaven.

The three most notable Non-Worlds involved in this Time War were Mictlan, a realm of pure ideas created by the Celestis to serve as their lair; the Eleven-Day Empire, a time-looped shadow-version of London serving as the base of operation of Faction Paradox; and the City of the Saved, (PROSE: The Book of the War) the realm of the timeship Compassion (PROSE: Of the City of the Saved...) which stood beyond the end of the universe. Additionally, the Thirteen-Day Republic was created by a breakaway arm of Faction Paradox in the eighth year of the War in Heaven in direct imitation of the Eleven-Day Empire. (PROSE: The Book of the War)

The Mandarin had been tracking Aboo-Fenran in the Arabian plains, but wasn't able to reach him before Fenran was "hurled" into a non-world, (PROSE: ) the Shadow Dimensions, which the Seventh Doctor sent him to after tricking him into growing progressively weak enough to be contained in a flask. (PROSE: )