While Nightmare moon/ Luna is on the moon she decides to keep a journal of all her thoughts. Also to keep her sanity. About 200 years into her sentence she finds a way to contact Celestia. Of course Luna's ecstatic about it. She even wrote down the spell and sent it to Celestia. But her dearest sister never responds which deeply saddens Luna, which triggers the Nightmare moon side of her comes out and Luna finds herself talking to the figure in her mind.