Celestia and Luna gave into their rage and became Nightmare Moon and Daybreaker then they ruled Equestria with a iron hoof. However you were the third sibling. You went over to visit and saw that they were different. They were planning on what to do now.

Daybreaker: "Their resistance is failing sister. I'm worried that they won't keep us entertained."

Nightmare Moon: "Of course. We're the two strongest Alicorns. What chance do those ponies have however seems we have a visitor."