This story is a sequel to The Snowpony
The Crystal Empire is old and strong and arrogant. It is the sole domain of ponydom outside the Sisters' rule, a preserved reminder of the days that passed long before the foundation of Equestria.
And it teaches its lessons well.
A story about the rise of King Sombra. Updates on a "I have no idea when" type basis. Dark and stupidly avoidant of proper nouns.
A Note On Sequels: None of them take place in the same location or carry the same themes. They're more a sort of loosely connected character arc for Princess Luna, starting with The Snowpony, that can be thought of as 'canonical' to one another.