Dalek Council

The Dalek Council, also known as the Supreme Council, was the governing body of the Dalek Empire and was based on Skaro under the Dalek Emperor, serving as their advisors. It was made up of the Dalek Empire's Supreme Daleks, who were designated Supreme Councillors.

Structure
Debate had emerged at the time of the publication of The Dalek Survival Guide as to whether every member of the Dalek Council held the title of Dalek Supreme, or an equivalent title like "Supreme Controller", or if only a singular Dalek held the position as the Emperor Dalek's second-in-command. (PROSE: Dalek Survival Guide)

Early history
The Supreme Council originally convened in chambers on the fourth Level of the City. (TV: The Daleks)

According to one account of the Dalek invasion of the galaxy, the Supreme Council, upon learning of the existence of the Dalek known as "Rusty", halted the war effort out of fear that his hatred for the Daleks could spread to other units, causing an existential crisis in Dalek High Command. When they eventually confirmed that it could not, they found his hatred too beautiful to extinguish and banished him to the Dalek Asylum. (PROSE: The Astounding Untold History of the Greatest Enemies of the Universe)

It seemed to have survived and was present when the Daleks tried to win the Great War. The Dalek Emperor and the Supreme Council determined that the Dalek Factor had to be researched so they could recondition humans with Dalek mentality throughout their history, potentially preventing the wars from ever happening. A Red Dalek acted as an emissary for the Council, overlooking the experiment being carried out by the blackmailed Second Doctor on Earth in 1866. (PROSE: The Evil of the Daleks)

Some time after the Daleks recovered from the resulting Dalek Civil War, (TV: The Evil of the Daleks) a Dalek Supreme with a gold-and-black casing was identified as "one of the Supreme Council". (TV: Planet of the Daleks) By one account, this Dalek Supreme was the head of the Supreme Council and the Emperor's second-in-command. (PROSE: Doctor Who and the Planet of the Daleks)

Dalek Wars
On the eve of the Second Dalek War of the 26th century, a Gold Dalek (TV: Frontier in Space) belonging to the Supreme Council (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) led a platoon of Daleks to meet on the Ogron homeworld. There, it ordered the Master's captives — including the Third Doctor, Jo Grant, General John Williams and the Draconian Prince — exterminated. However, the Master convinced the Daleks to leave the prisoners under his supervision until the Daleks' planned war began, to which the Daleks agreed and left the planet. (TV: Frontier in Space)

This allowed the Doctor to foil the Daleks' plans on Spiridon, (TV: Planet of the Daleks) resulting in the loss of the Dalek Supreme there and leading the remorseful Gold Dalek to organise a large-scale time travel mission to rectify its mistake, taking control of Earth in the 22nd century. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) This timeline was negated by an earlier version of the Third Doctor, leading to the destruction of the Gold Dalek by Shura at the Auderly House using a Dalekanium bomb. (TV: Day of the Daleks) The Time Lords believed this Dalek to be a subordinate "outpost commander" who deputised for the Dalek Supreme. (PROSE: Dalek Combat Training Manual)

According to human historians, after the failure of the Exxilon Gambit, the Supreme Council decided that the time for discretion had ended and launched a Dalek invasion of the galaxy, knowing that the galaxy was still reeling from the Daleks' space plague and any further delay would give them time to recover. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

The Supreme Council dwindled down more and over over the course of the Dalek Wars, until it was whittled down to a singular Supreme Dalek (PROSE: The Astounding Untold History of the Greatest Enemies of the Universe) who orchestrated the Daleks' master plan on Kembel. (TV: The Daleks' Master Plan) Other accounts claimed that the death of this Dalek Supreme on Kembel predated the Dalek Civil War. (PROSE: The Evil of the Daleks)

Civil War and beyond
When the Movellan War ended in defeat for the Daleks, the Dalek Prime and his Supreme Council retreated back to Skaro. By one account, the Black Dalek Leader knew that there was talk of overthrowing the Council and reforming the Dalek power scheme since the disastrous losses of the Movellan War. Acting on behalf of the Dalek Prime, the Black Dalek and the Supreme Council presided over the trial of Davros, who had been captured on Necros. At this time, there were some within the Dalek ranks, even within the Supreme Council, who felt that Davros could help the Daleks. The Black Dalek, however, anticipated that a rescue attempt would be made by "traitors" and saw that it was foiled, with Davros being seemingly executed by a matter transmitter. (PROSE: The History of the Daleks)

The Supreme Council existed as part of the Imperial Dalek side of the Imperial-Renegade Dalek Civil War. According to one account, at the end of the Civil War, Davros deserted his creations. This led to one member of the Council exterminating the other Supreme Daleks (PROSE: The Restoration Empire) and declaring itself the new Dalek Emperor of a once-again united Dalek race, (PROSE: The Restoration Empire, The Astounding Untold History of the Greatest Enemies of the Universe) which then fought in the Last Great Time War under his command. (PROSE: The Astounding Untold History of the Greatest Enemies of the Universe, TV: The Parting of the Ways) According to other accounts, the Emperor of the Daleks who led the Empire during the War and was ultimately obliterated by the Bad Wolf entity (TV: The Parting of the Ways) was in fact the leader of the Renegade Daleks, resurrected long after the end of the Civil War. (AUDIO: Restoration of the Daleks)

Post-Time War
At its onset, the five original members of the New Dalek Paradigm reorganized themselves into a new Supreme Council, led by the first Supreme Dalek, supported by the mysterious Eternal Dalek. The Strategist and Scientist respectively oversaw strategic and scientific endeavours, whilst the first Drone Dalek assumed command of the new Dalek Imperial Army. After acquiring the Eye of Time, the Supreme Council installed a new Emperor Dalek on a repopulated Skaro before launching an assault on time starting with Earth. However, the existence of this Emperor was erased when the Eleventh Doctor retrieved the Eye of Time. Later, the Supreme Council ordered the Dalek Project to be plotted throughout the history of Earth before it was stopped in World War I by the Doctor.

Though they ruled for centuries, they were eventually demoted to a token presence in the new Parliament of the Daleks after their repeated losses to the Doctor. When the Prime Minister of the Daleks had gone insane after remembering the Doctor during the Siege of Trenzalore, the Dalek Supreme exterminated him allowing it and its co-founders to resume control of the Paradigm until its fall. (PROSE: The Astounding Untold History of the Greatest Enemies of the Universe)

Alternate timelines
In one alternate timeline in which the Daleks invaded Earth in the 22nd century after a series of devastating wars, the Gold Dalek, the Black Dalek and their aids formed the High Council of the Daleks in Earth Sector One. (PROSE: Doctor Who and the Day of the Daleks)

In another alternate timeline where the New Dalek Paradigm conquered Earth in 1963, the Supreme Council Chambers were located in Kaalann. (GAME: City of the Daleks)

Behind the scenes

 * The Universal Databank claims that both the Black Dalek and Gold Dalek warlords were below the Emperor Dalek's Dalek Council.
 * According to The Dalek Handbook, a non-narrative source, the Daleks established a Council during their recovery after the Great Civil War on Skaro. At its head was a gold-and-black Dalek Supreme supported by Gold Commanders, replacing the earlier Black Dalek tier. Grey Daleks replaced the silver Daleks as drones, with designated Dalek Leaders reporting to the Commanders and the Supreme. The Supreme Council is apparently a separate entity from Dalek Supreme Command, which existed prior to the Civil War.
 * According to Aliens and Enemies, a non-narrative source, the Dalek Emperor's Personal Guard made up the "High Council of Daleks", of which the Dalek Supreme was also a member.