Tomte

Tomte started as a house spirit in the countries north of the Baltic Sea. Possibly the soul of the person who first cleared the lot for the house. He protected the house and family of farmers. But they were also easily offended. Cursing, rudeness, peeing in the barn, abusing the animals, or just changing how things were done were all good ways to get on his bad side. Being on his bad side could mean getting your ears boxed, dead livestock, tying cows tails together, turning things upside down, smashing things, or his venomous bite. A good way to get on his good side is to leave out some porridge for him. With butter on top. Gotta have the butter. On top. One common story has the butter being put in the porridge, Tomte killing the cow, then finding the butter, and hunting the countryside for an identical cow to replace the dead one.

A Tomte (a.k.a. Nisse) stealing hay

Honestly, he sounds like an all purpose threat. Be a brat and the Tomte will get you. Pull a prank and the Tomte will get you. Don't do things the way I do it and my father did it and his father did is and the Tomte will get you. Something went wrong! You must have made the Tomte mad! Much like how someone might say "you'll make the baby Jesus cry" today.

The myth changed as Christianity moved in. Tomtes would put your soul at risk or non-Christian rites were performed to get the Tomte there. Then, in the 1840's he started becoming the bearer of gifts. A painting of him made him look like an dwarven Red Cap or a tiny Santa Claus. He lives in a forest nearby or some neighboring country. He comes through the front door and delivers gifts directly. He's not overweight. Sometimes he rides a non-flying sleigh pulled by reindeer or goat, but he used to just walk.