Emperor's Personal Guard

The Emperor's Personal Guard was a Dalek organisation made up of Daleks dedicated to protecting the Emperor Dalek at all costs. They were normal Daleks, but with black domes; in addition, they sometimes possessed claws instead of standard manipulator arms or more powerful gunsticks opposite the standard.

History
For whatever reason, either as the Emperor's commanders or simply for their superiority, there were at least two Personal Guard in the execution party that chased the Doctor's TARDIS through eternity in a Dalek time machine. They were destroyed with the rest of the Daleks in the battle with the Mechonoids in the city when they landed on the planet Mechanus. (TV: The Chase)

The Emperor was always guarded by the personal guard in its throne room on Skaro. Their dedication to protecting the Emperor may have superseded their obedience, as they protected the Emperor from the attacking Humanised Daleks despite its commands to keep the fighting out of the room. (TV: The Evil of the Daleks) They were supported by Black Daleks and successfully crushed the rebellion, saving the Dalek race from destruction in the Great War. (PROSE: The Evil of the Daleks, COMIC: Bringer of Darkness, Children of the Revolution, TV: Day of the Daleks)

Although he was not the Emperor, Dalek X, the Dalek Inquisitor General, also had command of two black-domed guards during the Second Dalek War. They had two gunsticks and were destroyed at the end of the war when the Tenth Doctor blew up a disused refueling station on the planet Hurala, taking Dalek X's Exterminator with it. (PROSE: Prisoner of the Daleks)

During the Last Great Time War, the guards possessed a claw-like manipulator arm and some had a more powerful gunstick opposite the standard gunstick. The Emperor Dalek had four guards after surviving the Time War but were wiped out by the Bad Wolf in the year 200,100. (TV: The Parting of the Ways)

The guards were used by the second Emperor of the New Dalek Paradigm. At least one guard was present on the Dalek Flagship when the Daleks invaded Earth in 2106 using a piece of the Eternity Clock, but did not help the Emperor battle the Eleventh Doctor and River Song. This guard had red armour like the Dalek drones of the Empire, with a black dome. (GAME: The Eternity Clock)

The model of personal guard Daleks that were in use during the Great War were also present in the rebuilt Dalek city on Skaro, during the Twelfth Doctor's stay there. They were among the congregation of Daleks that captured and (apparently) exterminated Missy, Clara Oswald and the TARDIS (TV: The Magician's Apprentice).

Behind the scenes

 * The guards from TV: The Chase do not have black domes although their domes are clearly darker than those of the standard Daleks. As the serial is black and white, their true colour is unknown. The SFX Dalek merchandise identifies this Dalek as a "Guard Dalek". Its dome is coloured blue and the bands around its mid-section are gold, reminiscent of the standard Daleks from the film Dr. Who and the Daleks, the 1965 retelling of TV: The Daleks starring Peter Cushing.
 * Daleks with black domes are often seen taking part in battles and conflicts depicted in the Dalek Wars section of Doctor Who: Battles in Time magazines, as a result of promotional images of the black-domed Daleks being inserted into the scenery of the battles.
 * According to the non-narrative source REF: Doctor Who: Aliens and Enemies, the Personal Guard also made up the High Council of Daleks, of which the Dalek Supreme was also a member.