Cult of Skaro

The Cult of Skaro was an elite Dalek organisation that were "above and beyond the Emperor himself" and designed to "think as the enemy thinks". The Cult was thought to be merely a legend by the Tenth Doctor. (TV: Doomsday, PROSE: The Whoniverse)

Purpose
The Cult of Skaro were assigned the task of furthering the Dalek cause through the development of new and unorthodox ideas and strategies, while operating in complete secrecy. Dalek Sec claimed that it was created to "imagine new ways of survival". (TV: Daleks in Manhattan) Their willingness to adopt alien modes of thought was demonstrated by the fact that they had individual names, a concept most Daleks found unorthodox. Led by Sec, the black Dalek, they answered to no one, not even the Dalek Emperor, although they still respected him. (TV: Doomsday)

Origins
The Cult of Skaro were at first just four ordinary Daleks. Dalek Sec was the Dalek Commander of the Seventh Incursion Squad sent to wipe out the remnants of the Mechanoids which they succeeded in doing. Dalek Caan was an Attack Squad Leader of the Thirtieth Assault Group. Dalek Thay was the Commandant of Station Alpha, the most secret Dalek research facility. Dalek Jast was a Force Leader of the Outer Rim Defensive Battalion. After doing this all four of them were promoted to become the Cult of Skaro. They were given their names — making them some of the only Daleks with names — and Dalek Sec was chosen to be their leader. (PROSE: Birth of a Legend)

Last Great Time War
They were an elite order who were to think like their enemies in order to destroy them, although their original purpose was to imagine new ways of survival. During the Last Great Time War, they operated as a final strategic reserve. (TV: Doomsday) Knowing this was not a war the Daleks could win, (PROSE: The Whoniverse) they escaped into the space between universes, along with what they called the Genesis Ark, a piece of Time Lord technology. Having left the universe, they were not caught in the destruction of the Dalek fleet at the end of the war. (TV: Doomsday, Daleks in Manhattan, The Day of the Doctor)

Emerging from the Void
The Torchwood Institute's meddling began to open the barrier to the Void which had been broken down by the Cult's Void ship. Torchwood Tower, known to the public as Canary Wharf, had been built around the gap into the Void so that Torchwood One could study it and use its energy. When the Void Ship opened, the Cult exited the ship and declared war — or "pest control" — against the Cybermen that had invaded Earth from Pete's World, leading to the Battle of Canary Wharf while humanity was caught in the middle of the conflict.

They then opened the Genesis Ark and released "millions" of Daleks onto England. All these Daleks were sucked into the void along with the Cybermen, by the Tenth Doctor's intervention. The Cult escaped before being returned to the void, by using an emergency temporal shift. (TV: Doomsday)

Escape to New York City
After using the temporal shift, the Cult ended up in New York City in 1930. They infiltrated the construction of the Empire State Building and began what they called the "Final Experiment" — the creation of a new Dalek race. (TV: Daleks in Manhattan/Evolution of the Daleks) Inside the sewers below the Empire State Building, they set up a genetic laboratory and attempted to create new Dalek embryos. After the failure of this experiment, they tried thinking creatively, as the Cult was designed to. They devised a plan using Earth's greatest resource — its people. They placed Dalekanium upon the mast of the Empire State Building, intending to fuse the DNA of Daleks and humans using an incoming ray of gamma radiation from the sun. Dalek Sec tested this on Mr Diagoras, becoming a "human Dalek" hybrid, now with human thoughts and emotions. Dalek Sec wanted the Dalek-humans' to keep their human emotions, but the other Daleks, although bred to obey Sec, believed that this was against the Dalek cause. They changed the DNA to 100% Dalek and imprisoned Dalek Sec. Dalek Sec was later exterminated accidentally after the other Cult members fired their gunsticks at the Doctor.

The Doctor got in the way of the blast of gamma radiation and so infused the DNA with some of his own. The humans rebelled and killed Dalek Thay and Dalek Jast, before being killed themselves. The Doctor offered to help Dalek Caan — the last surviving Dalek — but instead of taking it, Caan used an emergency temporal shift to escape once more. (TV: Evolution of the Daleks)

The Last of the Cult
Caan was eventually able to penetrate the time lock on the Last Great Time War, from which he rescued Davros from his doomed command ship. Caan, however, became insane during his successful attempt at rescuing Davros. He came to view the Daleks negatively, and set in motion a chain of events that would destroy the New Dalek Empire. Caan, the last remaining member of the Cult of Skaro, was presumed killed when the Crucible was destroyed. (TV: The Stolen Earth/Journey's End)

Members of the Cult of Skaro
Dalek Caan, Dalek Sec, Dalek Thay and Dalek Jast were members of the Cult of Skaro. (TV: Doomsday) Some reports mentioned a Dalek Rabe, though - according to Justin Richards - these appeared erroneous. (PROSE: The Secret Lives of Monsters)

Behind the scenes

 * Throughout their appearances, Thay, Jast and Caan's recognition codes switch. In Doomsday, Dalek Jast's recognition code had two short lines on the bottom and middle and a long line on the top, and Dalek Caan's had two short lines on the top and bottom, and a long line on the middle; while in Daleks in Manhattan and Evolution of the Daleks, Jast's recognition code had two short lines on the top and bottom and no third line in the middle, and Caan's recognition code had two short lines on the middle and bottom and a long line on the top.
 * Thay, Jast and Caan are erroneously depicted as black-domed Daleks on the "Cult of Skaro" card from Doctor Who: Battles in Time.
 * A promotional still image from Doomsday, featuring the Cult of Skaro and the Genesis Ark, is used to depict Dalek invaders on a copy of the newspaper Daily Times in GAME: City of the Daleks. However, the invaders in the game itself are shown to be red Drone Daleks of the New Dalek Paradigm.
 * The Cult of Skaro and the later-introduced Volatix Cabal share heavy similarities (both being fanatic secret organisations of mutant Daleks created for the Time War, placed outside the Emperor's jurisdiction, and possessing creativity). However, no explicit link has been drawn between them.
 * The fact that there are only four of them to begin with is likely a reference to the fact that early on during the classic era's run the budget only allowed for four Dalek props to be fully created.

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