Fantasy Worlds

Have you ever seen a movie or read a book about some ordinary person, who stumbles across this magical world and they’re about to get eaten by some monster or something when all of a sudden this other human or magical creature comes in and saves you. Whenever I saw one of those scenes I thought about how unrealistic that world is. First off why would some other magical creature go out of their way and risk their lives just to save a creature they don’t know, because since they’ve grown up in that fantasy world they know that creature they’re fighting is dangerous and they’ve probably seen other creatures like you get eaten by it, so why would they go out of their way to save that person. Like if you saw an elf getting attacked by a grizzly bear you probably wouldn’t risk your life for the elf knowing you’ll most likely get killed as well. It just doesn’t make sense to me.