Eternal Dalek

The Eternal Dalek was a yellow, specialised Dalek of the New Dalek Paradigm. The first one was created by the Progenitor in 1941. Unlike its comrades, it had black, not grey, sense globes on its base unit battle armour.

History
The original Eternal was one of the five New Paradigm Daleks created when the three survivors of an encounter with the Doctor tricked the Eleventh Doctor into allowing them to activate the Progenitor device. It escaped through a time corridor with the others (the others being the white Supreme, blue Strategist, orange Scientist, and red Drone) and went on to help rebuild the Daleks. (TV: Victory of the Daleks)

The Daleks joined the Alliance formed to imprison the Eleventh Doctor in the Pandorica and save the universe from the cracks in time created from the TARDIS exploding. When they arrived at Stonehenge, 102 A.D. with the rest of the Alliance, the Eternal, the Supreme, and a Drone witnessed the Doctor being locked in the Pandorica. (TV: The Pandorica Opens) The Eternal Dalek was reduced to dust and stone along with the Supreme Dalek and the Drone Dalek following the total event collapse. This timeline would later be undone by the Doctor, restoring the Eternal and the other Daleks in their proper place in time. (TV: The Big Bang)

The normally silent Eternal would later relay the story of the Fall of the Eleventh to the Supreme after the the Question was heard from Trenzalore. This led to Dalek participation in the Siege of Trenzalore. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

Behind the scenes

 * Doctor Who Confidential revealed that the name of Eternal Dalek was provided by Steven Moffat in a "naming session" with Mark Gatiss. Neither had a meaning for the name, but Moffat opened in Confidential that he thought that the functionality of the Eternal would one day become critical to a story. The Dalek Handbook quotes Gatiss as saying "its exact function is a total mystery, but it's probably something to do with the Progenitor device and the continuation of the race."
 * Doctor Who The Official Annual 2011's feature on the New Dalek Paradigm makes the claim that there is only ever one Eternal Dalek and Supreme Dalek.
 * The Brilliant Book 2011 calls attention to the fact that the Eternal Dalek's colours are usually found on the most dangerous animals in the wild.
 * The Eternal Dalek is the only one of the five Progenitor Daleks to have black rather than grey orbs like the Gold Daleks from TV: Day of the Daleks and Frontier in Space.
 * The packaging of the action figure version of Eternal refers to the Dalek as The Eternal.
 * The Eternal Dalek is the only Dalek of the New Dalek Paradigm that has yet to appear in any material outside of the main TV series. A yellow Dalek (with dark grey rather than black orbs) is seen on the loading screens for City of the Daleks, and in the game itself. It is the only one of five Dalek variants absent in The Eternity Clock.
 * New Paradigm Eternal Dalek is an enemy in the Doctor Who: Legacy mobile game, which is not considered a valid DWU source.
 * In Doctor Who Live: The Monsters Are Coming! The Eternal claimed it could calculate and lock Time Parameters, this could mean the function of the Eternal is to turn points in time when the Daleks are close to succeeding into fixed points so they cannot be rewritten. If this is the case it likely means it is called the Eternal because it's function is to make sure the Daleks exist for all eternity.
 * All five archetypes of the New Dalek Paradigm feature in The Lego Batman Movie, appearing among the inhabitants of the Phantom Zone, alongside many famous villains from a number of fictional franchises. Like the others, they are unleashed upon Gotham City by the supervillain known as "the Joker" at the climax of the film, only to be defeated and sealed back inside the prison dimension. Their one line is the exclamation "Exterminate!", actually a piece of archive audio originally recorded by Nicholas Briggs for The Parting of the Ways.
 * In Dalek Hack, the player has the option to turn a Dalek's casing, shaped identically to the bronze Dalek, into any of the five colours of the New Dalek Paradigm.