your dark fantasy novel doesn't need a logic-based magic system it needs a bear with a human face
the human-faced bear principle of storytelling: the amount of people who will remember the exposition about the rules of magic or the history of elf culture inherently pales in comparison to the amount of people who will remember the scene where someone gets mauled by a bear with a human face
this isn't a call to necessarily include a literal bear with a human face (though you should at least consider it. obviously.) but pointing out that, while a lot of sf/f writing advice places heavy emphasis on fleshing out the small details of a fictional world as much as possible (which can be fine and valuable for many stories), there's often little attention given to the value of including effective "bear attack scenes", for lack of a better term; tense, scary, shocking, weird, or otherwise visceral scenes or concepts (the pale man, the chestburster, the sunken place, the raptors in the kitchen, artax in the swamp, the annihilation bear, the parasite basement, the blood test in the thing, etc) despite those having a significantly higher hit rate of making a story striking and memorable and recommendable to people
