Princess Luna remembers King Sombra a lot differently than the rest of Equestria. Sent to the newly discovered Crystal Empire, Luna learns of its citizens and of their King, soon finding it hard to part from him.
When she eventually does, her and Celestia find the Empire shut off from the rest of the world and under the rule of a tyrannical King. For his crimes, Sombra is destroyed and a thousand years passes by. The only problem is that Luna cannot forget the King she fell in love with all those years ago.
In secret, she will bring him back to her. Hopefully, it'll be the right Sombra that returns.