The fourth book in the Who Rules? Saga.
Luna and Celestia have decided to take a trip to get away from it all. Which means another princess is going to have to step up and take the reigns in Canterlot. Surely, nothing bad could happen while they were gone. Either to them or to Canterlot. (Hint: It happens to both groups.)
WARNING: This story contains graphic depictions of sex and powerplay. If you are offended by those things, do not read this.
You might also want to read the three previous Who Rules? stories to understand everything that is happening.
A duel between Celestia and Luna elicits an interesting response in the two sisters.
The sequel to Who Rules?. A wager between Celestia and Luna shifts the balance in Ponyville
The third book in the Who Rules? saga. Four ponies lives change, and Equestria hangs in the balance.
Luna and Celestia on the road, which means another princess takes over Canterlot.
Luna and Twilight discover something incredible, and the ramifications impact all of Equestria.
Princesses Celestia and Luna are having to adjust to life with a new princess in Equestria: Princess Chrysalis.
Luna now sits on the throne of Equestria, and Princess Chrysalis rules beside her--perhaps a little too closely for Celestia. On another Equestria, Twilight Sparkle discovers some truths of her own.