Shadow Dimensions

The Shadow Dimensions was a realm contained within a flask to which the Doctor banished Fenric in their battle in the 3rd century at the conclusion of a chess game. (DW: The Curse of Fenric) According to the ancient Arabian legend of their encounter, the flask contained the Seven Shadows. Like Fenric himself, the Shadows were a remnant of "the time before Time". (DWN: The Curse of Fenric)

The Celestial Toymaker was unimpeded in reaching the location to challenge Fenric to a game. Looking at the grey void and its shifting patterns, he described it as unimaginative, a non-world, and "a dimension of shadows and half-lives." (BE: Games)

The Demon described his home as being "a tiny backwater in a shadow dimension[...]bearing practically no resemblance to this physical universe." While the Shadow Dimensions were inside the flask, they may also have existed outside the universe, where the Demon was from. (AG: Sepulchre)