Western Fantasy: King in the North Starts with Conquering the Elves

(It's written for fun, so it's useless to put too many tags. You just need to know that Western Fantasy is ok if it has more female protagonists) Because I was addicted to reading a certain novel, I made a wish that I could travel to the Middle Ages and play with butter, but I made a wish, but I didn't say that I really wanted to go!