The Sycorax were a superstitious race of warriors and intergalactic plunderers (AUDIO: Harvest of the Sycorax; TV: The Christmas Invasion, et. al) native to the JX82 system. (WC: Monster File: Christmas) The Seventh Doctor considered the Sycorax to be "snarling space gangsters who smell like herrings and that's on a good day", (AUDIO: Harvest of the Sycorax) while Jack Harkness regarded them as a "nasty bunch" of "galactic scavengers" who were "always shouting and showing off". (WC: Monster File: Christmas)
Biology
The Sycorax had both an endo- and exoskeleton. The latter covered part of their head (giving them a skull-like appearance), leaving the rest of their skinless faces exposed to the elements. The exoskeleton could vary from a smooth, skull-like shape (TV: The Christmas Invasion) to a more jagged, horned shape. Some had long flowing hair. (COMIC: The Widow's Curse) The Sycorax also mounted horse-like creatures with the same biological facts, suggesting that they were related. (COMIC: The Widow's Curse)
Culture
The native language of the Sycorax was Sycoraxic, and in this language, the words for 'argument' and 'fight' were the same word. (AUDIO: Harvest of the Sycorax) The Sycorax practised slavery. They attempted to enslave humans in their Christmas Day invasion; (TV: The Christmas Invasion) whilst they deemed Christmas to be a "great time" to enslave humanity upon learning of it, their invasion did not depend on the holiday and simply happened to line up with the day. (WC: Monster File: Christmas)
The Sycorax's motto and battle cry was "Sycorax strong! Sycorax mighty! Sycorax rock!". (TV: The Christmas Invasion; AUDIO: Harvest of the Sycorax) They lived inside their starships, which were created from asteroids. (WC: Monster File: Christmas) The Sycorax followed the sanctified rules of combat and the ancient rites of combat. (TV: The Christmas Invasion) Sycorax men wore the ribs of their wives as a marriage bond. (COMIC: The Widow's Curse)
Religion
The Sycorax were a superstitious race who believed in magic and witchcraft. (TV: The Christmas Invasion) They worshipped the god Astrophia. (PROSE: The Final Darkness) Some Sycorax worshipped in churches. (COMIC: The Widow's Curse)
They also dedicated a huge room of their spaceships as a cathedral-like group worship chamber, regulated by a Sycorax priest. Within the chamber was a giant statue of Sycorax form, called a 'Wish of Bones', which was fashioned out of the skulls of the species that they had murdered and conquered. (AUDIO: Harvest of the Sycorax)
Technology
The Sycorax could detect energy signatures, letting them identify advanced technology. (TV: The Christmas Invasion, PROSE: The Final Darkness) They also had devices which resembled sea mines called Foraxi Yox. They functioned as black box recorders for spacecraft, allowing later viewings of events. (COMIC: The Widow's Curse)
The Sycorax used death whips which could destroy all the flesh in a body, leaving only burnt bones. During the invasion of Earth, they also used blood control. They understood, but did not speak, Earth languages such as English as this would "dirty their tongues". (TV: The Christmas Invasion, PROSE: The Final Darkness)
Sycorax spaceships were, in fact, a hollowed-out meteor and contained rooms such as a main hall, a grand worship chamber and sleeping quarters. The ship itself used the molten core of the meteor as its fuel. (AUDIO: Harvest of the Sycorax)
History
Early history
In 102, the Sycorax were among the races who joined the Alliance. They came to Stonehenge and helped imprison the Eleventh Doctor in the Pandorica to "save" the universe. (TV: The Pandorica Opens)
Sycorax invasion of Earth
In 2006, (TV: The Christmas Invasion) around the time of Christmas, (WC: Monster File: Christmas) a Sycorax asteroid ship entered the Sol system, (TV: The Christmas Invasion) after the Sycorax learned of Earth and its true value in precious stones, metals, minerals, and slaves. (PROSE: The Final Darkness) When the space probe Guinevere One crashed into them, they used the blood sample for blood control, threatening to kill every human with A+ blood unless they were given half the population as slaves. The Tenth Doctor, who had just regenerated, and his allies Mickey and Rose were inside his TARDIS. The Sycorax picked up a signal from the TARDIS' advanced technology and teleported them to their ship. The Doctor activated the blood control, knowing human survival instincts would break its hold. The Doctor challenged and defeated their leader in a sword duel, forcing the Sycorax to leave Earth and humanity alone.
However, as the Sycorax ship was leaving Earth, Harriet Jones ordered Torchwood to fire at it with a salvaged alien ray weapon, from a Jathaa sunglider, destroying it. (TV: The Christmas Invasion)
Aftermath
UNIT issued a press briefing where they confirmed the existence of aliens. (PROSE: Alien Life)
The wives of the Sycorax who invaded Earth came to the Sol system to find them, but found only the dust remains. They disguised their ship as an island called Shadow Cay, hypnotising all of humanity into believing it was discovered by Columbus. The Sycorax spent years searching for the ship's black box, the Foraxi Yox, and killed many humans, reanimating and controlling them as zombies, or human abstracts, to find it. In 2009, after discovering from the Foraxi Yox recording that humanity had betrayed the Sycorax, this group of Sycorax had a 747 aeroplane boarded with phage abstracts Gilfane Craw had created take off, intending to spread a virus carried by the abstracts that would stop death but leave humans in agony for centuries.
Donna Noble and Norah stowed away on the plane, and flew it back to Shadow Cay before it could reach London and spread the virus throughout humanity. Meanwhile, the Tenth Doctor overloaded the ship's magma-sculptor by making it attempt to copy the whole of Earth, and set its controls to take off before it exploded. (COMIC: The Widow's Curse)
Other events
In 2010, a Sycorax was seen at the Zaggit Zagoo bar when the Tenth Doctor came to visit Jack Harkness one last time before his regeneration. (TV: The End of Time) A Sycorax was present in the Maldovarium when Colony Sarff visited the establishment while searching for the Twelfth Doctor on behalf of Davros. (TV: The Magician's Apprentice)
The Sycorax returned to Earth in the late 21st century with hostile intentions, but left just as quickly. (PROSE: Snowglobe 7)
During the 41st century, the Astrophia Tribe died out during the Valhalla wars. The Tenth Doctor and Martha Jones met a lone survivor, a hunter collecting the last members of extinct species. (COMIC: Agent Provocateur)
In the future of the Human Empire, the Sycorax entered a secret deal with Pharma Corps, a pharmaceutical company that had the blood of every human sealed away in its vaults. With Pharma Corps controlling the emotions of every human in the Empire, they were able to give the Sycorax access to the blood of ninety nine percent of the human race. Just as the Sycorax were finding the means to enter its vault, the Seventh Doctor and new accomplice Zanzibar Hashtag, were able to trick the Sycorax by using the blood of a dead Sycorax in a blood controller, thus placing the whole fleet into a state of hibernation. Whilst under control, all of the Sycorax fleet were teleported back onto their ship and sent away. (AUDIO: Harvest of the Sycorax)
The Tenth Doctor told Martha that the Sycorax survived the end of the universe, along with humans and another unidentified species. (COMIC: Agent Provocateur)
Alternate timeline
In an alternate timeline, the Sycorax tried to invade Mandorla. (AUDIO: Enemy Lines)
Other references
In 1599, the Tenth Doctor, in the presence of William Shakespeare, noted how an animal skull reminded him of a Sycorax, inspring the name of the mother of Caliban in Shakespeare's The Tempest. (TV: The Shakespeare Code)
Intercepting a message from Harriet Jones, the Third Doctor, accompanied by Jo Grant and Mike Yates, arrived on 25 December 2006, where they witnessed the blood controlled masses and the Sycorax spaceship, ultimately returning home after seeing its destruction. Having followed them, the Master intended to ally with the Sycorax so that he could enslave Earth himself, only to be caught up in Roboform tinsel, preventing him from making contact with them. (PROSE: The Christmas Inversion)
The Sycorax was one of the 11 creatures who appeared in the hologram projection shown by the Atraxi as they were scanning Earth's history to check if it was protected. (TV: The Eleventh Hour)
The Great Intelligence mentioned, among others, the death of "the leader of the Sycorax" at the hands of the Doctor to dispute Madame Vastra's claim that the Doctor was never "blood-soaked". (TV: The Name of the Doctor) Their destruction was also mentioned by a version of Kate Stewart during negotiations between UNIT and the Zygons in the Black Archive. (TV: The Day of the Doctor)
Sometime in 2010, Mr Smith stated that his sensors were fully occupied by a Sycorax ship. He further mentioned that the Sycorax were not coming to Earth that day and there was nothing to worry about. (WC: Attic Padz)
A Sycorax, which the Doctor named "Clyde", was imprisoned in space along with the Thirteenth Doctor. It shared a cell with an Ood; aptly named Bonnie. One morning, when the Doctor was making her daily rounds through the prison, they growled and roared at her as she walked past their cell. (TV: Revolution of the Daleks)
Behind the scenes
Introduced in The Christmas Invasion, the Sycorax were created by writer Russell T Davies, who was credited for their reprisal in The Magician's Apprentice. Although appearing in Revolution of the Daleks, Russell T Davies remains uncredited.
Russell T Davies' original concept for the Shadow Proclamation scene in The Stolen Earth included an appearance by several Sycorax, but his plans to feature a "rogues gallery" of alien races in the scene fell through; ultimately the Judoon were the only returning race featured.
William Shakespeare also created an unseen character called 'Sycorax' in what is widely assumed to be his final solo play, The Tempest.
The Visual Dictionary
The non-narrative source Doctor Who: The Visual Dictionary gave further information about the Sycorax.
They could live up to four hundred years. The Sycorax were organised into the Sycorax empire, divided into large tribes.
Sycorax had pride, honour, and some respect for the rules of war. Leadership was earned by trials of strength and combat. They wore skull-helmets to impress their enemies, and red-robes as a sign of leadership. They would take trophies of body parts such as bones, skin or hair from conquered races. Some wore belts of Judoon skin.
Sycorax had many ancient rituals involving suns and moons. They left a hole in their space-ships for the solar and lunar light to get in.
Despite being spacefaring, many Sycorax relied on simple weapons, such as swords and knives, generally adorned with trophies.
The Sycorax used asteroids fitted with an All Speed Inter-System Type K engine as spacecraft. The first of these asteroids was the home world of the Sycorax, the Fire Trap. At some point in Sycorax history, an alien spaceship crashed into the Fire Trap. They used its engines to turn their asteroid into a spaceship. More asteroids were added by other tribes, creating the Sycorax Armada. They used teleporters to move to and from the ship.
Many tribes left their home region in their asteroid ships to explore space, to conquer and enslave other planets, expanding the empire.
The tribe that invaded Earth in 2006 was called the Halvinor tribe.
The Time Traveller's Almanac
According to the non-narrative source The Time Traveller's Almanac, they had the capability to translate the languages of other species.