Black Dalek Type VIII

A distinct Black Dalek casing model was contemporary to the bronze Dalek drones, designated the "Type VIII Dalek" by the Time Lords. Though they noted the black casing as being "like the Supreme Dalek", this was only true for the earlier models, as this Black Dalek was a contemporary subordinate to a red-and-gold Supreme Dalek. (PROSE: Dalek Combat Training Manual)

Characteristics
This Black Dalek casing shared the refined shape of the bronze Daleks. Unlike earlier Black Dalek models, both the shoulder slats and the sense globes were black as well. (TV: Army of Ghosts)

Incidentally, the Dalek Survival Guide had believed that the Dalek drones who served in the Time Paradox Incident were black complete with slats and globes, (PROSE: Dalek Survival Guide) though other accounts established them as grey Daleks with grey slats and black globes, (TV: Day of the Daleks) with a Black Dalek supporting the Gold Dalek. (PROSE: Doctor Who and the Day of the Daleks) In any case, the Defence Drones created under the watch of the Reconnaissance Dalek were black complete with slats and globes. (TV: Revolution of the Daleks)

History
After seeing to the extermination of the Mechanoids on Magella, the Dalek Commander of the Seventh Incursion Squad was one of four high-ranking bronze Daleks summoned to Skaro by the Dalek Emperor who, in anticipation of the Last Great Time War, assembled them into the Cult of Skaro. The Commander, who the Emperor named Dalek Sec, was transferred to a new black casing made of metalert. (PROSE: Birth of a Legend)

Active during the Time War, the Overseer had a black Dalek casing, with his dome sporting a red eyepiece lens and very short luminosity dischargers. The Overseer's weapons platform notably featured several long-range extendable claw manipulators, including from the ball joint where a suction arm was found on standard Daleks; the Overseer's weapons platform also featured a spherical scanner, with a blue light, on his left-hand side. The Dalek creature itself was "impure" and ultimately exterminated by its own subordinates, who deemed it to be more trouble than it was worth. (AUDIO: Planet of the Ogrons)

Having escaped the Time War in the Sphere, the Cult of Skaro emerged in the post-Time War universe where they were embroiled in the Battle of Canary Wharf. The intervention of the Tenth Doctor led the Cult to escape via an emergency temporal shift (TV: Army of Ghosts/Doomsday) to Manhattan in 1930, where they launched the Final Experiment. Opening up his casing, Sec merged with the human Diagoras to become a Human-Dalek hybrid. His transformation complete, Sec stepped out of his Black Dalek casing. Shortly after, Sec was usurped by his subordinates when he attempted to work with the Doctor, and ultimately exterminated during the invasion of Manhattan. (TV: Daleks in Manhattan/Evolution of the Daleks)

When the Daleks of the New Dalek Paradigm reintroduced the bronze casings, Black Daleks were also reintroduced as lower-ranking officers. Some Black Daleks dubbed insane by the Dalek Parliament were inmates of the Dalek Asylum. They were destroyed when the Parliament fired on the Asylum after the Eleventh Doctor shut down the planetary force field. (TV: Asylum of the Daleks)

One such Dalek oversaw the progression of the Dalek Project and was connected to Survey Ship Sigma before the ship's destruction in a battle of the First World War. The survival chamber survived and the Black Dalek was destroyed when the Eleventh Doctor overloaded the Dalek ship in 2017. (COMIC: The Dalek Project) Its position was very similar to that of the earlier Chief Strategist. (COMIC: The Only Good Dalek)

Black Daleks, accompanied by Red Daleks, had occupied the Starbane when the Twelfth Doctor and Lumpy arrived with the intention of destroying the vessel along with the Orb of Fates. All the Black Daleks were destroyed when Starbane exploded. (GAME: The Doctor and the Dalek)

Another Black Dalek was among the many variants of Daleks present in the rebuilt Dalek City on Skaro. Davros intended to turn these Daleks into Dalek/Time Lord hybrids. They were destroyed in an attack by regenerated decomposing Dalek mutants which destroyed the City. (TV: The Magician's Apprentice/The Witch's Familiar)

A Black Dalek once chased the Twelfth Doctor through a metallic corridor and attempted to exterminate him. However, the Doctor used his sonic screwdriver to close sliding doors just as the Black Dalek was crossing a gateway. The two heavy metal doors thus held the confused Dalek in place like a vice, while the Doctor made his escape. (WC: A Hero like the Doctor)

Invalid sources

 * Leading a group of six bronze Daleks, the Black Dalek Sec is the end boss to be deleted in Parliament Square by the Cybermen using their energy blasters in the game Daleks v Cybermen. Upon his deletion, the Black Dalek announces that it is the end of the Daleks as the Cybermen prevail in the Battle of Canary Wharf.
 * The Eleventh Doctor Interactive Story introduces the Children of Davros, a Dalek faction rivaling the New Dalek Paradigm with ranks consisting of bronze Daleks led by a Black Dalek. They are depicted using archive footage of Dalek Sec and the Cult of Skaro from Daleks in Manhattan.

Merchandise

 * A figurine of Dalek Sec was released with the fourth "Rare Dalek" issue of Doctor Who: Figurine Collection magazine.