Scandinavian folklore has alot of monsters that could be used for enemies in the game. Imagine for example coming across a river and finding the Näck or a Brook Horse. You could also have a bunch of Nisses as friendly npc's. The Lindworms are giant snakes that look kinda like wingless wyverns but with front legs instead of hind legs. The wights were tiny underground tricksters that lived under houses, before Tolkien used the word for his underground ghost. There's also all kinds of Rås you could use, although the Forest Rå (also known as the Hulder or Huldra) is the most famous. One of the creatures that doesn't have an English wikipedia page is a huge fire-breathing boar with burning eyes and razor sharp fur (this is apparently where the English name "razorback" comes from), that right there is one of the coolest creatures I've ever heard of. And that's only some of the creatures, Scandinavian folklore contains many more, often overlapping with each other.
STOP! COOKIE TIME