Zygon The Zygons were a race of metamorphic humanoid s . They originated from the planet Zygor , but often tried to migrate away from it . ( PROSE : " The Bodysnatchers " ) Biology . Zygons were solidly built humanoid s with large , cone - shaped heads . Their heads , arms and torsos were covered in suckers , and they had deeply inset faces . Zygons had dark red blood and spoke in a gurgling whisper . They were stronger than human s and apparently more long - lived , their lifespan continuing over Earth centuries . ( TV : " Terror of the Zygons " ) They also had an earthy , iron odour and the ability to sting people with venomous barbs on their palms . These stings could stun , maim or kill . They left large welts on the affected area . ( PROSE : " Sting of the Zygons " , PROSE : " Doctor Who and the Loch Ness Monster " ) They also had the ability to create a process to transform members of other species into Zygons , with the side effect of creating a telepathic link between the new Zygon and the one that induced the change . ( HOMEVID : " " ) They had venom sacs located in their tongue s . ( TV : " The Day of the Doctor " ) Young Zygons were called hatchling s and were slimy and pale with shorter limbs . Hatchlings were mute , but much faster than adults . ( PROSE : " Sting of the Zygons " ) Zygons had a deeply ingrained fear of fire . ( PROSE : " Doctor Who and the Loch Ness Monster " ) They could be easily hypnotised by a clock ' s swinging pendulum . ( GAME : " Destiny of the Doctors " ) Zygons were hermaphrodite s that could reproduce asexually . At the start of their lives , they had an almost white colour , had no suckers and were more feminine and graceful . They became orange - coloured , were covered in suckers and became more stocky and masculine in appearance after being sterilised . The greatest rank a Zygon could attain was " warrior engineer " . To become a warrior engineer any Zygon must undergo sterilisation , a process which makes them more aggressive and single - minded . ( PROSE : " The Bodysnatchers " ) Zygons were able to produce electricity bolts from their hands that could stun humans or other Zygons or disintegrate them into piles of hair and skin . ( TV : " The Zygon Invasion " ) When used on the Twelfth Doctor , however , he was slightly phased , but otherwise suffered no ill effects . ( TV : " The Zygon Inversion " ) Technology . Zygon technology was partly biological , with an organic look . This was exemplified by the Skarasen , a large , cybernetically enhanced creature from their home world . Zygons were also known to depend upon the lactic fluid of the Skarasen for their survival . ( TV : " Terror of the Zygons " ) Their use of organic ships was well known . ( PROSE : " Alien Bodies " ) One of the most important Zygon discoveries was their use of body - print s . Usually , the Zygons would capture a specimen , such as a human , and put them in a special receptacle . A Zygon could then take the form of this specimen , mimicking both voice and appearance . This body - print needed to be renewed every two hours , while the prisoners were kept alive but unconscious . ( TV : " Terror of the Zygons " ) However , in some circumstances they were able to adopt the shape of the specimen without keeping them in a receptacle , although they still needed the specimen alive . ( TV : " The Day of the Doctor " ) At some point they gained the ability to keep the shape of a deceased specimen , as long as they did not need any more information from them . They also gained the ability to forge a telepathic link with another being and take the form of a someone from their memory . ( TV : " The Zygon Invasion " ) Though they generally took the forms of humanoid s , they could also mimic creatures of diverse sizes and shapes , such as dog s , cattle and horse s . ( PROSE : " Sting of the Zygons " , TV : " The Day of the Doctor " ) A Zygon who could no longer transform was known as a Zynog . ( AUDIO : " Death in Blackpool " ) If a Zygon was killed while disguised , it would remain in that form as a corpse . ( HOMEVID : " " ) To control the Skarasen , the Zygons used Trilanic activator s . Zygons frequently used molecular dispersal to get rid of corpses . Their ships tracked the life - signs of the Zygons and would bring the corpse back to the ship if a Zygon was killed . ( TV : " Terror of the Zygons " , PROSE : " Sting of the Zygons " ) They also made use of a type of nerve gas to render humans unconscious . ( TV : " Terror of the Zygons " ) Another Zygon discovery was called the " amber sleep " , which was a type of suspended animation . ( PROSE : " Sting of the Zygons " ) Culture . Zygons were divided into clans , each with a different culture . ( AUDIO : " The Zygon Who Fell to Earth " ) Zygon warlords fought in elaborate shape - shifting duels using the bodies of other creatures held captive . ( COMIC : " Rest and Re - Creation " ) A Zygon High Command organised Operation Double on Earth with the Unified Intelligence Taskforce before being violently overthrown and replaced by a faction of radical Zygons called Truth or Consequences which sought to usurp human ity . ( TV : " The Zygon Invasion " ) Zygon Queen s ruled over individual planets . ( PROSE : " Lords and Masters " ) Zygons measured distance in remar s . ( TV : " Terror of the Zygons " , PROSE : " Sting of the Zygons " ) Zygons were evidently rather fond of board games . ( PROSE : " The Bodysnatchers " ) History . Early history . The Zygons joined Rassilon in the Alliance of Races against the Hyperions . ( COMIC : " The Hyperion Empire " ) After the Hyperions were defeated , the Alliance then went on to purge the universe of other threats to universal harmony , one of those threats being Count D ' if of the Cybock Imperium . ( COMIC : " Gangland " ) Loss of Zygor . According to one account , the Zygons were originally at war with the Xaranti . During this war , both the Zygon homeworld , Zygor , and the Xaranti home planet s were destroyed . ( PROSE : " The Bodysnatchers " ) Another account claimed that their planet burnt in the first days of the Last Great Time War . ( TV : " The Day of the Doctor " ) Refugees created a refugee fleet , and the ship on Earth was contacted . ( TV : " Terror of the Zygons " ) 2nd century . In 102 , the Zygons were among the races who joined the Alliance at Stonehenge . They came to Stonehenge and helped imprison the Eleventh Doctor in the Pandorica to " save " the universe . ( TV : " The Pandorica Opens " ) Before the 12th century . At some point before the 12th century , a Zygon ship was damaged and forced to land on Earth near Devil ' s Punchbowl in Scotland . They had a Skarasen with them which , though still an infant at that point , provided them with the lactic fluid they needed to survive . ( TV : " Terror of the Zygons " ) 16th century . In 1562 , a Zygon force was on Earth and investigated by the Tenth Doctor , one of them impersonating Elizabeth I . After the real Elizabeth killed her impersonator , the Zygons implanted themselves into stasis cube s , planning to wait until Earth was more suitable for conquest . ( TV : " The Day of the Doctor " ) 19th century . In the late 19th century , a Zygon became a member of a travelling freak show and later impersonated Queen Victoria . ( AUDIO : " The Barnacled Baby " ) A Zygon ship was trapped under where the Savoy Hotel was . During the grand opening in 1890 , Zygons replaced half the staff , but the Eleventh Doctor , Amy Pond and Rory Williams stopped them . ( TV : " The Power of Three " ) The Eighth Doctor , Sam Jones and George Litefoot encountered a group of Zygons in London in 1894 . ( PROSE : " The Bodysnatchers " ) 20th century . Another ship from Zygor arrived on Earth in 1909 . Though they had brought two Skarasen , their minds were damaged by the solar radiation during the destruction of Zygor . One was killed during repairs . Though the Zygons attempted to conquer Earth anyway , starvation and the Tenth Doctor forced them to abandon their plans . ( PROSE : " Sting of the Zygons " ) In the 20th century , a Zygon spaceship landed in a Brentford quarry . The Zygons of Devil ' s Punchbowl decided to take over Earth and physically adapt it to an environment more suited to their species . UNIT and the Fourth Doctor stopped them , freeing the Skarasen . ( TV : " Terror of the Zygons " ) In 1981 , UNIT had to deal with over a hundred Zygons who survived a previous invasion . ( PROSE : " The King of Terror " ) In 1984 , the Eighth Doctor and Lucie Miller encountered a Zygon who was impersonating Lucie ' s aunt , Patricia Ryder . ( AUDIO : " The Zygon Who Fell to Earth " ) In December 1985 , a Zygon landed in Antarctica , near UNIT Arctic base Skywatch - 7 . Several people stationed there were killed , but the survivors were able to drive it into the icy water where it perished . ( COMIC : " Skywatch - 7 " ) Circa 1999 , a Zygon invasion of Earth was prevented by UN military advisor Guy Dean . ( AUDIO : " Homeland " ) 21st century . In the late - 20th and early 21st centuries , the Zygons Torlakh and Kritakh were deployed on Earth , where they took the forms of Bob Calhoun and Michael Kirkwood respectively . They then began to go to nuclear power plant s around the world , so that 70 years later the planet would be more suited to Zygons and they could hand the planet over to a Zygon invasion force . The plan backfired when Kritakh began to believe he was Michael Kirkwood , and began to see a psychiatrist about his dreams of being a Zygon . His doctor , Lauren Anderson , was turned into a Zygon by Torlakh , and she went to see him again . However , she decided to help Michael stop Torlakh . They put the real Bob Calhoun and Michael Kirkwood in the hospital , and Torlakh left to continue his life on the run . Lauren , however , also was forced to live on the run , when Torlakh killed many of her co - workers at the hospital . She left , but not until after she killed Torlakh while he was in her form . ( HOMEVID : " " ) In 2008 , the Eighth Doctor and Lucie Miller again encountered the Zygon who impersonated Patricia Ryder . ( AUDIO : " Death in Blackpool " ) In the early 21st century , the Zygons that were frozen in 1562 woke from their stasis cubes and infiltrated UNIT , gaining access to the technology in the Black Archive . To prevent them using the technology , Kate Stewart activated the countdown to a nuclear warhead beneath the Archive . Before the countdown reached zero , the Tenth , Eleventh and War Doctor s temporarily erased the memories of the original Kate , Osgood and McGillop , as well as their Zygon impersonators causing them to forget which ones were human and which were Zygon . Both Kates cancelled the detonation , and the humans and Zygons were able to create a peace treaty between them . When no one was looking the Zygon copy of Osgood slipped the original ' s inhaler back to her . ( TV : " The Day of the Doctor " ) Two years later , a rebel faction of Zygons , led by Bonnie , began to undermine the ceasefire . Bonnie had taken the form of Clara Oswald , and was determined to expose the 20 million Zygons living on Earth and find a land of their own , ( TV : " The Zygon Invasion " ) but this was defused by a contingency developed by the Twelfth Doctor involving two Osgood Box es . ( TV : " The Zygon Inversion " ) 22nd century . 150 years after Kritakh and Torlakh were brought to Earth , the Zygon invasion force was still due to arrive on Earth . ( HOMEVID : " " ) 28th century . In 2765 , Zygons attempted to melt Earth ' s polar icecaps , but were stopped by INITEC ' s Vigilante laser defence satellite s . ( PROSE : " Original Sin " ) 36th century . Circa the early 36th century , a group of Zygons on Ganta 4 infiltrated the New Eden colony so they could use their spaceship to evade Earth security and invade humanity ' s homeworld . The plan was defeated by colonist Christopher Shaw , and the Zygons were all killed . ( AUDIO : " Absolution " ) Undated events . On Shontaa , the Zygon warlords Anktra and Kestral fought a duel using a variety of host bodies . The Fourth Doctor and Leela ended the duel by freeing the host creatures which the Zygons were mimicking . ( COMIC : " Rest and Re - Creation " ) , using the power of the planet Siralos , transported some Zygons and other adversaries to the Doctor ' s TARDIS to stop the Graak from saving the imprisoned seven incarnations of the Doctor . ( GAME : " Destiny of the Doctors " ) The Divine Empress had Zygons under her command . ( PROSE : " Genocide " ) River Song once angered Zygons by greeting them with , " What ' s up , suckers ? " ( GAME : " The Eternity Clock " ) A yellow Zygon was present at Garage 10 . ( COMIC : " The Ministry of Time " ) The Ninth Doctor defeated a Zygon who took the form of Rose ' s grandmother . He then disabled it ' s body - print technology . ( PROSE : " Little Rose Riding Hood " ) Alternate timelines . In an alternate timeline created by the Black Guardian where the First Doctor never left Gallifrey , and became Lord President , the Zygons were one of many aliens that invaded Earth , and fought over the planet with other races against the Silurian s and Sea Devil s . This timeline was negated when the Seventh Doctor retrieved the Key to Time . ( COMIC : " Time & Time Again " ) In an alternate dimension in which the Doctor ' s adventures existed as a fictional TV show called " Doctor Who " , a fan dressed as a Zygon was present at a " Doctor Who " convention which the Eleventh Doctor visited with Ally in 2013 . ( COMIC : " The Girl Who Loved Doctor Who " ) References . When re - united with the Fifth Doctor , the Brigadier remembered the Zygons among adversaries he had fought as head of UNIT . ( TV : " Mawdryn Undead " ) The Seventh Doctor used " the Zygon gambit with the Loch Ness Monster " as an example to Ace of the alien invasion s that humans had managed to rationalise away or forget . ( TV : " Remembrance of the Daleks " ) The Seventh Doctor said that when he felt depressed , he would make clay models of Zygons to cheer himself up . ( PROSE : " Human Nature " ) When the telepathic Emily Fairfax read the mind of the Hypothetical Gentleman , a Zygon was among the images she saw . ( COMIC : " Hypothetical Gentleman " ) Mayor Me considered her hidden trap street , which had existed in London for at least a century prior to Operation Double , to be a more favourable way of housing alien s on Earth as opposed to the settling of the Zygons amongst humanity . Later , in a desperate gambit to prevent Clara Oswald from sacrificing herself , the Twelfth Doctor threatened Me to relinquish the Quantum Shade on Clara or he would expose her trap street and bring UNIT and the Zygons down on it . ( TV : " Face the Raven " ) The protection granted to Zygons on Earth was exploited by other shapeshifters such as Ballon , a Lorr , who posed as a Zygon in order to avoid detection by UNIT only to be captured by the Governors . ( TV : " The Metaphysical Engine , or What Quill Did " )