Servitor (Pyramids of Mars)

The Osirians' Servitors, also known as servicers, and referred to as Osiran service robots by the Doctor, were obedient constructs resembling mummies. They were used by such Osirans as Sutekh and Horus as servents and henchfolk.

Nature
Although the Fourth Doctor referred to the Servitors he met as as "Osiran service robots", believing that they were machines (TV: Pyramids of Mars) just as Bernice Summerfield did, (AUDIO The Pyramid of Sutekh) Horus explained that they were actually made of flesh, albeit artificially grown. Their wrappings were not a mere disguise, but were soaked in a chemical which had some part to play in keeping their biology stable. (AUDIO: Ozymandias)

History
The Servitors were created by Anubis for use by Horus's side in the civil war between the partisans of Horus and the partisans of Sutekh. (AUDIO: Ozymandias) Before the schism and the abandonment of the Ship of a Billion Years, most Osirians had used indentured slaves from the lesser species as servants, rather than artificial beings. (AUDIO: The Ship of a Billion Years) One such Servitor served as Horus's boatman. (AUDIO: Ozymandias)

After Marcus Scarman was killed by Sutekh in his tomb, Ibrahim Namin brought several Osiran Servitors to an old priory in England in sarcophagi. The constructs were confined to a locked wing of the house but had been active for some time. They killed Collins, the butler, when he entered the room. Namin activated the constructs once more in order to search for and destroy Dr. Warlock and his rescuers, the Fourth Doctor and Sarah Jane Smith.

After Namin was killed by Sutekh's puppet, the animated corpse of Scarman, the constructs were used as workers and guards. They set up a force-field around the house and constructed an Osiran war missile to free Sutekh from his bonds. They also killed several people on the property, including a poacher named Ernie Clements who attempted to interfere.

Scarman took one of the Servitors to the Pyramid of Mars on the mission to find and destroy the Eye of Horus. As part of one of the Pyramid's tests, two of Horus's Osiran Servitors (distinguishable by having certain parts of their bindings coloured gold) would appear when an intruder was trapped in a Tachotron Crucible: one robot — referred to by Horus as "the Guardian of Lies" — would lie, i.e. give a false indication; while the other — called "the Guardian of Truth" — would tell the truth, i.e. point truthfully. Another one of Horus's constructs also guarded the chamber where the Eye of Horus was located, and fought with Scarman's robot over the Eye. (TV: Pyramids of Mars)

In 2010, UNIT Underbase contained an Osirian Servitor salvaged from a past alien invasion of Earth. (COMIC: The Age of Ice)

The Guardian of Truth and Guardian of Lies robots were encountered by Bernice Summerfield in a pyramid on Mars. The Guardian of Lies used the voice of Bernice's dead husband Jason Kane when interacting with Bernice, as it said it would calm her down. (AUDIO: The Pyramid of Sutekh) Ace and Benny found one whilst looking for an Eye of Horus. (AUDIO: The Vaults of Osiris)

Osiran Servitors were present on the Shining Horizon. (COMIC: Old Girl)

Technical information
The Servitors were powered by a cytronic particle accelerator in the shape of a pyramid that was located on the back. They took voice commands from whoever they were programmed to obey. A special ring was used to activate them or countermand their orders. They were also extremely strong, able to manhandle humans with ease, and could easily strangle someone. (TV: Pyramids of Mars)

Other references
In the video game Happy Deathday, played by Izzy Sinclair on the Time-Space Visualiser, a Servitor was among a host of "every single enemy" that the Doctor had ever defeated, who were assembled by the Beige Guardian and pitted against the Doctor's first eight incarnations. (COMIC: Happy Deathday)

In 2007, when Sarah Jane argued with Rose Tyler about the monsters they had encountered, Sarah Jane mentioned "mummies" as one of the many she had encountered. (TV: School Reunion)

When the Skith Leader scanned the Tenth Doctor's mind, a Servitor was among the alien creatures shown to him. (COMIC: The First)

Behind the scenes
According to The Brilliant Book 2011, a book that contains non-narrative based information, Winston Churchill encountered the Third Doctor at Omdurman in the Sudan on 3 September 1898, whilst the Doctor was battling what appeared to be an Osiran Servitor.