Sometimes an idea is vast and complicated, sometimes it’s not. And often, that’s the problem keeping a concept from getting off the ground. There’s not enough to carry a story. That’s the main issue with today’s refuse from the scrapheap.
300-inspired military fantasy, where the protagonists use huge lightweight shields that magically resist the faster you try to move them.
This was all I left myself to go on. Basically, the Battle of Thermopylae with standard-issue fantasy dwarfs instead of ripped Hollywood Spartans.
That said, the basic idea isn’t hopeless. How could it be? It’s barely the start of an idea. If it were a more interesting scrap of an idea, maybe I’d have rolled it into something by now. But I’ve got either a beardy remake of 300 or police with magical riot shields. Maybe that ends up as a throw-away aspect of some larger story, but it’s nothing to base a series, or even a book, around.
Of course, I present it to emphasize that it’s important to keep all your story ideas, good and bad. You never know when one might combine with another like Legos to produce something better than either part alone.
(but probably not this one)