When Twilight is alone in her castle, she gets a friendly visit.

In an alternate universe, there is no Luna nor a Celestia. Just Daydream Sun. But now, Nightmare Moon is arriving happily from her prison, and all the ponies will be joyous over her arrival.

What Celestia and Luna did when Luna was on the moon was a mystery. Until now

Sapphire was surely in for a ride when she met Princess Luna, and now visiting Canterlot just got better.

Twilight Sparkle has just become a Princess! But now, she needs advice on how to be one, but Nightmare Moon returns mysteriously from Luna's Shadow, so Luna and Twilight team up to save Equestria from eternal darkness!