Medusa Cascade

The Medusa Cascade was a colourful nebular region of space and the location of a rift in time and space which was sealed at some point by the Doctor.

It was located "halfway across" the universe from Earth. (TV: The Battle of Ranskoor Av Kolos)

Appearance
The Cascade was nebulous in appearance, containing what appeared to be clouds of coloured gas. (TV: The Stolen Earth) In addition to the space-time rift at its heart, (TV: Journey's End) it also contained at least fifteen "broken moons". (TV: The Sontaran Stratagem)

History
The Medusa Cascade was visited by a young Doctor when he was "just a kid" of ninety-years-old. (TV: The Stolen Earth) According to one account, it was on this occasion that the Doctor sealed the rift as part of his practical temporal technology exam. (PROSE: Report on Term's Work)

According to other accounts, however, the Eighth Doctor was the one who sealed the Medusa Cascade with a modified De-mat Gun during the Last Great Time War, (COMIC: The Forgotten) at the same time as faced the Dalek Emperor on the Cruciform. (PROSE: The Secret Diary of the Master)

The Fourth Doctor and Romana later visited the Medusa Cascade. (PROSE: City of Death)

In one potential timeline of the Last Great Time War, Livia and Narvin saw the Medusa Cascade burn to nothing as a result of becoming creator of the Daleks. (AUDIO: The Master's Dalek Plan)

During the invasion of the Kaiphos Occlusion, other engagements between the Daleks and Time Lords opened in the Medusa Cascade which General Trave hoped might distract the Dalek forces. (AUDIO: Desperate Measures)

The Medusa Cascade was the place to which Davros's New Dalek Empire moved twenty-seven planets. The planets could not be found by regular means, as they were out of temporal synchronisation with the rest of the universe by one second. (TV: The Stolen Earth) Davros placed them there so that when his reality bomb was set off, it could penetrate the Cascade's space-time rift and spread the bomb's destructive force across every possible timeline and all of existence. (TV: Journey's End)

This act led to an invasion of Earth, one of the required twenty-seven planets. (TV: The Stolen Earth) It ended with the near-total destruction of the Daleks by the Meta-Crisis Tenth Doctor and (with the help of the Doctor and his companions) the return of all of the planets to their correct locations in time and space. (TV: Journey's End)

Behind the scenes
Explaining how Henry van Statten was unfamiliar with the Dalek he named Metaltron, The Time Traveller's Almanac suggested that the Van Statten Incident took place in a timeline where the Cult of Skaro did not emerge from the Sphere resulting in the Earth not having been transported to the Medusa Cascade since the personal timelines of both the Doctor and the Dalek race had not progressed to the point where those events occurred.

Rhaeadr Fedwsa Cascada Medusa Cascade de Méduse