Great Catastrophe (The Exterminators)

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The Great Catastrophe was a devastating event triggered by Kalendorf that engulfed the galaxy Mutter's Spiral a few hundred years after the 36th century, destroying virtually all of the civilised planets and plunging the galaxy into a dark age.

Prelude

Inspiration in legend

Kalendorf told a legend from the Knights of Velyshaa that all of Sancroff's lieutenants took a vow of "Victory or Death" and remained fiercely loyal to him, except for one lieutenant named Satiricius, who plotted to overthrow him. When Sancroff learned of her impending betrayal, he met with her in private. Immediately after that meeting, Satiricius returned to her castle and killed all of her fellow conspirators, then herself. It was rumoured that this was a psychic compulsion impressed on Satiricius by Sancroff during her vow. (AUDIO: Dalek War: Chapter Four)

Dalek invasion

The Daleks invaded Mutter’s Spiral from the Seriphia Galaxy and began the Second Great Dalek Occupation, fighting the Earth Alliance. (AUDIO: Invasion of the Daleks) Within a decade, they had conquered almost everything, including Earth. Susan Mendes, the "Angel of Mercy", used a broadcast on Yaldos across the entire Dalek Empire to use a trigger phrase, which her accomplice Kalendorf had been telepathically implanting in every slave they had met, to begin a rebellion across the galaxy. This threw the Empire into chaos. (AUDIO: “Death to the Daleks!”) 

Three months later, the Dalek Emperor activated Project Infinity and made contact with Daleks of a parallel universe. These Daleks judged the Daleks to be guilty of the worst crimes they had ever witnessed and declared war on them, allying with the Earth Alliance. (AUDIO: Project Infinity, Dalek War: Chapter One) To escape capture by the Alliance Daleks, the Emperor transferred itss mind into Suz, who had been placed in suspended animation after beginning the rebellion.

After six years, Kalendorf decided to betray the Alliance Daleks, having decided that they were simply a more outwardly benign dictatorship. He arranged Suz's recovery from Alliance Dalek custody and had her give a broadcast as the Angel of Mercy to turn the Earth Alliance against the Alliance Daleks. A truce was formed with the Enemy Daleks and Kalendorf surrendered Suz to the Dalek Supreme so the Daleks could recover their Emperor. (AUDIO: Dalek War: Chapter Three) After years of fighting, the Alliance Daleks finally retreated back to their universe as their leader, the Mentor, predicted the war would eventually lead to the extinction of all life in Mutter's Spiral. A fragile truce remained between the Earth Alliance and the Daleks. (AUDIO: Dalek War: Chapter Four)

The Catastrophe

Kalendorf launched the "Great Catastrophe" to finally free the Mutter's Spiral from Dalek control. (AUDIO: Dalek War: Chapter Four)

With the fragile peace holding, Kalendorf travelled alone to Dalek-occupied Earth to meet the Emperor. To his surprise, the Emperor had decided to remain in Suz's body, now fully possessing her. As Kalendorf had anticipated, the Emperor revealed its intent to soon attack the outnumbered humans. He grabbed hold of it and used his telepathy to reawaken Suz's mind briefly to activate a trigger phrase he had implanted in her before surrendering her: "Victory or death".

This triggered a signal through the Dalek Empire's command net, which Suz was connected to via the Emperor, ordering all Dalek technology to self-destruct. The Daleks were annihilated and much of the galaxy was devastated in the process, with whole star systems being destroyed and countless lives lost, but the Mutter's Spiral was finally free of the Daleks. (AUDIO: Dalek War: Chapter Four)

A single Dalek outpost in Seriphia survived the Catastrophe by channelling the destructive signal into a single Dalek drone. The drone absorbed the entire command net, including the minds of the Emperor and Suz. It was declared the new Dalek Supreme. (AUDIO: The Demons)

Aftermath 

Kalendorf survived the Catastrophe. Decades later, he encountered the Eighth Doctor at a museum on Vega VI dedicated to the Occupation. (PROSE: Museum Peace) He eventually returned to Velyshaa, where he left telepathic imprints warning about the Daleks. (AUDIO: Dalek War: Chapter Four)

In time, the event became the subject of legends that were passed throughout the planets of the galaxy. These legends spoke of a figure known as the "Dark One" or the "Bringer of Death" who was responsible for the Catastrophe. (AUDIO: Dalek War: Chapter Four) The galaxy took centuries to recover to the point of resuming interstellar travel. (AUDIO: The Exterminators)

The Daleks rebuilt in Seriphia under the leadership of the new Supreme and eventually returned to Mutter's Spiral approximately 2,500 years after the Catastrophe. (AUDIO: Dalek War: Chapter Four, The Exterminators)