Black Dalek Leader

The Black Dalek Leader, usually just referred to as the Black Dalek, was the earliest Black Dalek in existence. It was the Dalek Emperor's warlord (COMIC: The Secret of the Emperor) and second in command, taking charge of the Dalek City on Skaro in the Emperor's absence. (COMIC: Plague of Death) It was senior to other Black Daleks that came into existence later (TV: The Dalek Invasion of Earth, AUDIO: Masters of Earth) in the same way the Red Dalek Leader was senior to other Red Daleks. (COMIC: Eve of War)

Biography
The Black Dalek Leader was summoned by the Emperor to deal with Zeg after he challenged the Emperor's authority. It's weapon was unable to penetrate Zeg's metalert casing. (COMIC: Duel of the Daleks)

When the Daleks developed space travel, the Emperor led an invasion force off Skaro to conquer other planets, (COMIC: The Amaryll Challenge) leaving the Black Dalek in charge of the Dalek City. When the Daleks were threatened by the outbreak of a rust plague, the Black Dalek was infected in such as way that it could be used as a vessel to transmit the plague to other Daleks. The Emperor returned to Skaro to deal with the situation. The Emperor's guards chased the Black Dalek away to protect the Emperor. The Emperor then found the Black Dalek by the Brain Machine, rusting away, resigned to its fate, ashamed as it was of letting other Daleks die. The Emperor claimed the Black Dalek was too valuable to lose and sent it to the recasting furnace to be repaired. (COMIC: Plague of Death)

Later, after its recovery, the Black Dalek led a force of Daleks to the planet Phryne in search of new technologies as war with the Mechanoids became evermore certain. They successfully occupied the planet, although many Phrynians went into hiding to form a resistance movement. (COMIC: The Archives of Phryne)

The Emperor called a meeting with the Black Dalek and a Red Dalek when the presence of the One in a Million Dalek threatened to cause a civil war. (COMIC: Shadow of Humanity) Both were also present on the Emperor's ship when the Daleks first ventured into the Sol System. (COMIC: Return of the Elders)

In the 40th century, (COMIC: The Brain Tappers) the Black Dalek Leader presided over the re-election of the Dalek Emperor. The Black Dalek obliterated the entire Red Extra-Galactic Squadron when their commander denounced the Emperor for failure to defeat the humans. (COMIC: The Secret of the Emperor)

Behind the scenes

 * In The Chase, Mission to the Unknown and The Mutation of Time (the Target novelisations of The Chase, Mission to the Unknown and The Daleks' Master Plan), author John Peel implies that the Black Dalek present in those stories is the Black Dalek Leader. In The Mutation of Time, the Dalek Prime considers the Black Dalek "irreplaceable", echoing the Emperor's thoughts from Plague of Death. This does not factor in the Black Dalek destroyed in The Dalek Invasion of Earth, set in between both stories, unless it only applies to the Black Dalek Leader, which was mostly just called the Black Dalek. If this was Peel's intention, it would not be the only elements from The Dalek Chronicles included by Peel in his novelisations; Red Daleks and the Dalek Prime resembling the Golden Emperor are other examples.
 * Because The Dalek Chronicles went through frequent art shifts, the Black Dalek Leader often changes colour and design between stories. It is black and silver in Duel of the Daleks, black and gold in Plague of Death, and black, gold and silver in The Archives of Phryne making it resemble the Black Dalek from Dr. Who and the Daleks, the non-canon retelling of The Daleks starring Peter Cushing.