One assumes they engaged in some kind of training for that (and live in a supernatural world that has such power available), but that doesn't make the human species different from Earth human in that world.
In any case, RPGs generally explain themselves more completely and in detail than film, because the medium allows for it. Look at most any RPG based on a licensed fantasy or science fiction property. They almost always provide more detail than the film or TV show does, because players ask questions, and because RPGs have the time and space required to do so.
So, taking one well known RPG that has had time to explain things...
... insert previous questions on lava
... insert previous questions on a hit in combat
... insert previous questions on encumbrance rules
... insert previous questions on how learning new skills related to killing things