We writers of fantasy have a dangerous fixation on the Big Dumb Thing.
BDTs are those objects, locations, and phenomena that carry a feeling of awe and mystery. Larry Niven’s Ringworld, the Monolith of Arthur C. Clarke and The Wall in George R.R. Martin’s Song of Ice and Fire. They wow the audience, and provide iconic images that serve as symbols for entire bodies of work.
Furthermore, a BDT can be abstract - such as Robert Jordan's system of the One Power, or countless fictional technologies present in science fiction.
The one thing a BDT cannot be, is a character - and that means that a BDT can never be enough to drive a story.
You probably already knew this. Most writers of sci fi and fantasy come across this caution early and often - and yet still I meet writers who are ‘building their world’ before they write their story.
Wrong order! If you want to tell people about “your world” then you need to draw their interest with compelling stories and, especially, interesting characters. Until you weave it into a compelling story and demonstrate how it affects the lives of characters we love (or hate), your Big Dumb Thing is just a glorified prop.
Another common stumble for these world-builders is to 'design' their characters just like they design their world (sci-fi and fantasy is overrun with engineers, it seems). If you approach creating a character like assembling a robot, you’ll end up with something that shares a few traits with a machine: artificial, lifeless, and driven by the mission to destroy mankind.
You can't pick a bunch of traits and try to glue them together into a character. You'll end up with a monstrosity of hard angles and poorly fitting parts, where the cracks between his "brutal upbringing" and "love of puppies" are glaringly obvious.
Real people aren’t engineered - they grow. Let your characters do the same. You may have an idea for their personality, but then you need to decide how they got that way. It is a common quirk for writers that they know their characters' back-stories, even if the reader never finds out. This is a quirk of necessity - this history informs the character. In effect, it mimics the natural development of a real person.