The Krampus—a half-humorous counterpart to Saint Nicholas, who snatches bad children at Christmas—came to my attention via artist Kathleen Jennings' post on Krampus Krackers from the Tiny Owl Workshop. In 2014, the workshop produced a limited run of hand-made, letterpressed crackers for sale at chosen bookshops and cafés in Australia. Each contained an illustration and a grumpy flash fiction. Imagine a short story about clever, disgruntled twelve-year-olds who hear about them and decide to make their own to hand out to friends and family! It could be an antidote to icky sentimentality and over-commercialism at Christmas.
The Krampus tradition, which is centered in Alpine Austria and Bavaria, is related to various other dark winter figures and mummers everywhere. Troupes are made up of young men in scary, elaborate costumes who run through city streets or go house to house. They carry switches and menace onlookers. It can get pretty rowdy, even cruel, and another realistic story idea might move aggressive danger—as could a magical story about a real Krampus. (I'd rather stay on the witty side.)
In the late 19th C, a postcard craze fixed the image of the devil-like figure in its present form. Lately, as the internet spreads interest in the Krampus, it is evolving to adapt to other locations, other circumstances. For a quick history, you can read Al Ridenour's article The Truth about Krampus at Atlas Obscura or his full-length book with many photographs of costumes, masks, and troupes: The Krampus and The Old, Dark Christmas Roots and Rebirth of the Folkloric Devil.
For pictures of ten festivals that feature the Krampus or related figures, see 10 Traditional Winter Festivals in Europe at The Guardian.