Sycorax

The Sycorax were a superstitious race of warriors and intergalactic plunderers.

Biology
The Sycorax had both an endo- and exoskeleton. The latter covered part of their head (giving them a skull-like appearance), leaving the 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 Sycoxax also mount horse-like creatures with they same biological facts, suggesting that are related.(COMIC: The Widow's Curse).

Culture
Sycorax men wore the ribs of their wives as a marriage bond. (COMIC: The Widow's Curse)

The native language of the Sycorax was Sycoraxic. The Sycorax practised slavery. They attempted to enslave humans in their Christmas Day invasion. (TV: The Christmas Invasion)

Religion
Though they had advanced technology including interstellar space travel and energy whips, the Sycorax were still 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)

Technology
The Sycorax could detect energy signatures, letting them identify advanced technology. (TV: The Christmas Invasion, PROSE: The Final Darkness) They also had crystal ball-like devices which functioned as Black Box recorders, allowing later viewings of events. (COMIC: The Widow's Curse)

The Sycorax used energy 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. (TV: The Christmas Invasion)

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)

At Christmas 2006 a Sycorax asteroid ship entered the Sol system. 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) The Sycorax used an on-board energy detectors to detect this threat. They realised that they would die and so placed a curse upon Earth. (PROSE: The Final Darkness)

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)

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 Sycorax returned to Earth in the late 21st century with hostile intentions but returned home 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)

The Tenth Doctor told Martha that the Sycorax survived the end of the universe, along with humans and another unidentified species. (COMIC: Agent Provocateur)

Other references

 * In 1599, the Tenth Doctor, in the presence of William Shakespeare, noted how an animal skull reminded him of a Sycorax. (TV: The Shakespeare Code)
 * 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)

Behind the scenes

 * 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.
 * In terms of the voodoo-themed nature of their technology and helmets made from the bones of unknown animals, the Sycorax are somewhat similar to Faction Paradox.
 * The Sycorax resemble the Kaleesh race from Star Wars, mainly due to their similar appearance, i.e red skin, their bone masks, war-like nature.

The Visual Dictionary
The non-narrative source REF: 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 REF: The Time Traveller's Almanac, they had the capability to translate the languages of other species.