Celestia and Luna married the mane six, now they have a harem and a honeymoon to deal with. In all honesty, happily ever after isn't all it's cracked up to be. At least there'll be room for orgies.
As the newest Princess in Equestria, Twilight Sparkle discovers that there are new experiences to be had. As she learns about her new body, she discovers a certain element shared by pegasus ponies. Wings.
Luna, strangely enough, receives a letter from Princess Twilight Sparkle. From the letter she can discern two things. One, Twilight definitely has a drinking problem. Two, she really loves her. And a third can go to being extremely kinky.
Twilight gets called into a meeting with Luna and Celestia. The kingdom is hurting for money and there's only one way to get rich quick. Celestia is going to have to film them making porn.
Certain alicorns have no regard for the rules of space and time. An astral sub-dimension becomes a potent weapon in what appears to be a divine prank war. Shining Armor hits the sauce.
Twilight is angry. Normally, a more calm approach would be useful, but when a pony... When a pony commits THAT, well, the chips are off the table. Justice must be extracted.
Twilight Sparkle wakes up to a very unwelcome idea. Now she needs to find a way to clear it out of her mind. Because if she falls asleep before it's gone, the Princess of Dreams will get to see that idea for herself.