Chapter-8: The spell.
Twilight runs into Cadence's study room and says- “Cadence, I found something! Come with me!”
Cadence says- “I'm coming.”
Twilight teleports them to Sombra's secret room and shows Cadence. She says- “Look what I found. There was a lever on the wall, and I pressed down on it and then the wall moved to show all these crystallized ponies. I found a book on the bookshelf that shows how to undo the spell, but two Alicorns have to do it.”
Cadence looks at all the crystallized ponies and says- “This is terrible. It's a good thing you found the counter-spell for it. Where is the book?”
Twilight gives Cadence the book. After Cadence reads it, they both get ready to do the spell. They concentrate hard on what they want to do and at the same time, two bright lights come from their horns and goes onto each crystallized pony. All the ponies are not crystallized anymore and Twilight and Cadence teleports each pony into the throne room. Twilight teleports down there one last time to lock the door. She does it and then walks back up the stairs, since she is too tired to teleport. Once she reaches the top, she sees Cadence telling each pony that they were turned into crystal statues, and were left like that for over a thousand years, and that King Sombra was defeated and that they are safe.
After Cadence finishes talking, all the ponies leave. Cadence turns around and tells Twilight- “So that's why there aren't any unicorns or pegasi in the Crystal Empire. They were all crystallized.”
Twilight says- “I was wondering too, why there were hardly any unicorns or pegasi in the Crystal Empire.”
Cadence asks Twilight- “Are you going to go back to Ponyville now?”
Twilight replies- “Yes, I'd love to stay, but I have to go back home.”
Cadence says- “Oh. Well, if you're going to leave now, the next train to Ponyville leaves in 10 minutes. Promise to visit soon?”
Twilight replies- “I'll visit as soon as I can. It's a promise! Bye, Cadence.”
Cadence waves and says- “Bye Twilight. See you again soon!”
Twilight waves and then runs to the train station. She reaches there and gets on the train just a few minutes before it leaves.