So I like to envision the Crystal Empire as an actual like, empire, with 6 individual kingdoms(city states? idk) that radiate around the royal palace, where the Empress would settle disputes between them, manage trade and commerce, and keep up the magical barrier that prevents the cold and wandering/lingering magic and creatures to invade.
Originally each ‘kingdom’ were more like very small tribes of ponies with they’re own Kings/queens that would fight and try to take over each other for they’re food and supplies until around 1500 years before Luna’s return, when one of the Queens succeeded in taking over and making them work together instead of against, therefore becoming the first Empress. It wasn’t until 50-60 years before Luna’s banishment that the unicorn Empress Amore would take the throne, and use her own love-based magic and an enchanted heart shaped crystal to cast the Barrier around all 6 kingdoms, thereby uniting them into what is now the Crystal Empire.
Soon after the Empire was founded and Crystal Fair established, the tyrant King Sombra usurped the throne and enslaved the crystal ponies before being banished by the sisters and cursing the Empire to disappear for the next
1000 or so years.
Cadence, as she is in canon, is a descendant of Empress Amore, and has inherited not only her love based magic, but also has the ability to wield more powerful and corrupting magics without succumbing to insanity or greed, which is what allowed her to ascend to alicorn status with the help and guidance of Celestia.
i don’t even know why i’m talking about this no one’s gonna read this shit lmao
I never did fully understand while a single city was called an “Empire”, I kinda like Op’s headcanon in the image description here about the sections of the city having once been separate buroughs. ^^