The Tenth Doctor described Zygons as “Shape-shifting aliens from outer space!” Powerful, technologically advanced and with the ability to mimic the appearance of other living creatures, these horrors without a home had a deadly arsenal – everything from venom sacs in their mouths to the Loch Ness Monster!
When the Fourth Doctor first encountered the Zygons they should have been a species that deserved our sympathy. Their home planet had been destroyed and as their spaceship was damaged, they were stranded on Earth. They needed lactic fluid to survive although luckily this was produced by their ancient alien creature, the Skarasen, a massive water-based cyborg that humans knew as the Loch Ness Monster…
The Skarasen will destroy you all!"Broton
But these Zygons intended to take over our planet and enslave humanity; they proved ruthless adversaries, attempting to kill the Doctor and attacking a terrified Sarah Jane Smith with a pitch-fork. They thought nothing of kidnapping humans so they could take their ‘body print’ and replicate their physical appearance and even intended to use the Skarasen in a brutal show of strength against mankind.
The Doctor and UNIT defeated the Zygons on this occasion but the shape-shifters joined forces with many of the Time Lord’s old enemies during the events of The Pandorica Opens. And later, although we didn’t see the confrontation, the Doctor made it clear that he defeated a number of Zygons in Paris, 1890, when many of them had disguised themselves as workers at the Savoy Hotel…
In The Day of the Doctor it was a case of more Zygons, more trouble. One tried to impersonate Elizabeth I but the feisty monarch was apparently able to deal with the impersonator herself. ‘I may have the body of a weak and feeble woman,’ she explained when recalling their tussle, ‘but at the time, so did the Zygon!’
The Zygons who gained access to the Black Archive proved more dangerous. The weaponry in UNIT’s secret vaults would have given them a frightening level of power and Kate Stewart was prepared to sacrifice London if it meant keeping this awesome arsenal out of alien hands. The Doctors were able to wipe the memories of humans and Zygons alike who had gathered in the Archive but as the groups’ two leaders negotiated a settlement, Osgood and the Zygon that had taken her form realised which was the human…
In a moment that inspired optimism, these two former enemies opted to keep silent and let the parties arrive at a peaceful solution. However, these first signs of friendship were soon forgotten when some time later, a rebel faction of Zygons on Earth began to undermine the ceasefire.
The rebel faction, led by Bonnie, a Zygon who had taken the form of the Doctor’s companion Clara Oswald, were determined to expose the 20 million Zygons living on Earth and find a land of their own. These Zygons had a number of new abilities, they were now able to forge a telepathic link with other humans and take on the form of their loved ones from their memories as a way of defending themselves from attack. They also no longer needed to secure the host in Zygon pods to maintain the host’s physical form (provided they did not need the memories of the host). And, as a new form of attack, the Zygons were able to release brief electrical charges from their hands to stun their enemies or melt them down to balls of hair and skin!
Thanks to an emotional appeal from the Doctor at the eleventh hour, all-out war between the Zygons and the humans was averted, and the ceasefire was restored.