This is a diary of the 1000 year imprisonment in the moon Nightmare Moon had to endure. She goes through her time in her prison watching Equestria thrive under her elder sister Princess Celestia. She placed every little thought of her imprisonment in it and filled its pages with thoughts and plans for the future, if she were to be released from her cell. But when Twilight Sparkle comes to visit Celestia, and in a bit of commotion, Luna takes one of Twilight's books thinking it was the diary. When Twilight realizes she has it, she can't help but look inside.