This story is a sequel to King Sombra's Rise and Fall
An eon ago when King Sombra overtook the Crystal Empire with powerful magic, Princess Celestia feared that a malicious unicorn might threaten Equestria, too. Thus, she passed laws with the secret intention of preventing unicorn threats to the kingdom. She locked many powerful spells in the Canterlot Archives, took over magical education, and prohibited unicorns from raising the sun as they once did. Prince Blueblood discovers this and leads a revolt to establish a unicorns-only kingdom.
Proofread and edited by SpaceCommie. This story now has a sequel, Brother Against Sister. Part of the Unicornverse.