I had a thought. I bought the book called Journal of the Two sisters. It basically the diary Luna and Celestia shared and it talks about things like the founding of Equestria and all that. The Unicorn Kingdom still existed after Equestria was formed and the King Queen and Princess Platinum from The unicorn Kingdom talked with The Two Sisters often. My thought is What if King Sombra wasn't a part of the Crystal Empire at all? Because that would Mean he would be Emperor Sombra not King Sombra. The even addressed him as "The Unicorn King" once. What if King Sombra was from the Unicorn Kingdom instead?