Even in her retirement Princess Luna had still felt obligated to walk through dreams and fix every pony's- now every creature's- nightmares. She did not mind doing this every sunset to sunrise but lately her sister Tia felt that her night time job was wearing on Luna. They were both in retirement and yet one still continued to work her hooves dead.

So, after some consideration, Princess Luna agreed and took a trip down to Canterlot to pass down her knowledge to their successor, Twilight.