Gloricious

 was a human colony planet. When climate change threatened the colony, the colonists were saved by three aliens who purportedly used their mental abilities to keep the climate steady. The aliens learned of Christmas and decided to make every day Christmas, demanding sacrifices from the colonists. The Fourth Doctor exposed the aliens as liars and blackmailers, and he showed the colonists that the aliens had been using technology to keep the climate steady. (PROSE: Christmas Every Day)