Jolnir

 was an alien who crashed on Earth during pagan times. He was worshipped as a god and gained energy from this belief. When humans stopped worshipping him, his power became dormant.

During Christmas of 1966, Tobias and Kristianna Blackstone, the last of Jolnir's believers, attempted to bring him back into power. They used sacrifice (of turkeys), a black crystal, and the story of Jolnir - provided by advertising for their soft drink - to bring about a widespread belief in Jolnir. Jolnir was defeated when the Seventh Doctor and Jasmine Deering created a new advertisement depicting Jolnir in a comical way. (PROSE: Christmas in Toronto)