Zygon

The Zygons were a race of humanoids encountered by the Fourth Doctor, Sarah Jane Smith, and Harry Sullivan at Loch Ness, Scotland. The Zygons had been trapped on Earth for hundreds of years, living near the loch, and controlled a large reptilian creature called the Skarasen, which was mistaken by the locals for the mythical Loch Ness Monster.

Physical characteristics
Zygons are solidly built humanoids with large, cone-shaped heads. Their heads, arms and torsos are covered in suckers and they have deeply inset faces. Zygons have dark red blood and speak in a gurgling whisper. Zygons are stronger then humans and can live for several centuries. (DW: Terror of the Zygons) Zygons also have a very deeply ingrained fear of fire. (DW: Doctor Who and the Loch Ness Monster)

Technology
Zygon technology is partly biological and all their technology has a half-grown look. This is shown by the Skarasen, a large creature from Zygor which has been cybernetically enhanced.

One of the most important device of the Zygon is their shapshifting ability. The Zygons can capture a Human and put them in special receptacles. They can then take the form of the human, but they need constant bio-scan checks in order to maintain the illusion. Because of this, the subjects are kept alive but unconscious during the whole process. This process copies both the appearance and the voice of the subject, though the Zygon's actions may give them away. (DW: Terror of the Zygons)

History
The Zygons were originally in a war with the Xaranti. During this war, both of their home planets were destroyed, though the refugees were able to create a refugee fleet. One of the war-ships was damaged and eventually made it to Earth, where the Zygons hid out for hundreds of years, waiting for news from Zygor. When they learned that Zygor was destroyed, they decided to take over Earth for a new home-planet. (DW: Terror of the Zygons)

Culture
Little is known about the Zygon culture, since the only Zygon shown were soldiers. It is known they measure sound in Remars. (DW: Doctor Who and the Loch Ness Monster)

Major appearances

 * Terror of the Zygons
 * The Bodysnatchers