The Zygons first appeared in the 1975 serial "Terror of the Zygons", in which they planned to conquer Earth following the destruction of the Zygon homeworld. One of their spacecraft, commanded by warlord Broton, crash-landed into Loch Ness in Antiquity. The Zygons used a Skarasen (a creature that provides milk for their sustenance and which had become known as the Loch Ness Monster by humans) to attack an energy conference in London. The plan was foiled and Broton and his crew were killed, due to the intervention of the Fourth Doctor and the United Nations Intelligence Taskforce (UNIT). The Skarasen retreated into the depths of Loch Ness.