For many generations, ponykind has been the slave race of the Centaur Empire. Providing them with warm bodies for mating, "willing" subjects for scientific testing, and ponypower for massive engineering products. Hundreds of thousands have died over the centuries, and magic has faded to obscurity over time, known only by the highest of the centaur lords. The horns of unicorns have been snapped off at birth for hundreds of years, after all. No unicorn can use magic.
Till one book-worm finds a book that changes everything.
( This is a "for fun" fic, exploring pony sociology, magic, building a nation from the ground up, a non-evil S- oop, almost gave it away there! And of course, a magical society versus a technological one. )