Formula for doors
The formula for doors was a complex ritual which manipulated the data sets of the universal fabric to generate a gateway out of nothing. It was more easy to perform in areas with "semantic density", meaning places where events of emotional significance had occurred in number — such as a temple or a battlefield.
The Minister of Chance, a renegade Time Lord, had his TARDIS revoked as punishment for misusing his powers by the Seventh Doctor. (WC: Death Comes to Time [+]Loading...["Death Comes to Time (webcast)"]) As a result, he began to rely on the formula for doors to travel the universe, a much more cumbersome process which did not allow short range travel, only journeys between planets or to alternative planes of existence such as the Frost Bridge or the river Hex. The technique was also known to the Horseman, although during his many years of exile on the Broken World he lost his finesse, only being able to create crude, unstable metallic-looking doors. (PROSE: The Minister of Chance [+]Loading...["The Minister of Chance (novelisation)"], AUDIO: The Broken World [+]Loading...["The Broken World (audio story)"], etc.)
