Luna was able to avoid being seen by Celestia while going through the maze, and she exited the maze without Celestia knowing. She then ran and hid behind a bush to take a rest, "What are we going to do? Celestia will surly catch us, and make our punishment quite severe..."
Luna looked like she was about to give up, but then she heard a familiar voice, "Oh, come now, Luna. You can't give up that easily," Luna looked and saw the spirit of the night right in front of her.
"Spirit! You have come back!" She then noticed that the spirit now had two arm-like protrusions on its form, "Spirit, where did you obtain those odd appendages from? I know they were not there the last time we had met."
"Well, when you stood up to Celestia, the power of the night increased, which in turn affected my form."
"Oh, we see. Well, maybe then you can help us to escape from Celestia before she punishes us!"
"Escape? Why in the world would you want to escape? Don't you want your night to stay in the sky?"
"Yes, I do, but Celestia is far more powerful than we are. She has already beaten us in our throne room duel. We do not stand a chance against her..." Luna lowered her head in shame.
"Well then, it looks like you could use my help to defeat her."
Luna looked back at the spirit, "What could you do to aid us? Even we doubt you are powerful enough to defeat my sister in combat."
"Well, not by myself, but if you lend me some of your magic, I may have a way for you to become even more powerful than Celestia!"
Luna was shocked, "More powerful than Celestia?? How is it possible for you to perform such a feat??"
"It's easy. Just lend me some of your magic, like I said, and I'll make you the most powerful pony in the world!"
Luna looked unsure of what she wanted to do, "We...we're not sure..."
"Not sure?? You deserve to have your night be seen by all! And you also deserve to take Celestia's place as ruler of Equestria! Someone as cruel as her doesn't deserve to be ruler!"
Luna then thought back to what Celestia told her in the throne room, and how upset and angry it made her feel, "Okay, spirit. We will do as you say to do," Luna then started it disperse her powerful magic out of her horn. The spirit then used his powers to hold her magic in one spot. He then started to merge his powers with hers, forming two different objects with the magic. Luna did not know what he was doing, but she knew it was either accept his help, or face Celestia, which she knew she could not do. After some time had passed, the spirit had completed what he was doing with the magic, and showed to Luna what he had created, "Spirit, what be those objects you have constructed with our magic?"
"Well, my dear princess," he said as he showed her the object he was holding with his left appendage, "This object is the Moon Plate. It harnesses the power of the moon to increase your strength, so you can stomp harder, run faster, and fly faster," and then he looked at the other object he was hold with his right appendage, "And this is the Night Helmet. It harnesses the power of the night to increase your magic powers to even higher levels than Celestia!" Luna was amazed by the power of these objects, "With these two objects, you will be able to overpower Celestia and take your rightful place as ruler of Equestria!"
"Oh my, well, we agree that these objects are indeed powerful, spirit, but…"
"But?" The spirit said, bemused.
"It's just…we are uncertain as to if we are able to control such power."
"Unsure?? How can you be unsure? You're the princess of the night! There's nopony in the world who could control it better than you!"
Luna still looked unsure, but then she heard Celestia calling for her, "Luna! Where are you?? Come out right now so we can end this once and for all!" Celestia wanted to try and work things out with Luna, but Luna mistook her words for a kind of punishment.
Luna felt scared of Celestia, but she also felt her rage building up inside her again, "All right, spirit, Place the objects upon us, so we can be the ones to end this once and for all."
"As you wish, my princess," The spirit said as he placed the Moon Plate and Night Helmet on Luna. Luna watched the spirit as he placed the plate upon her first, and then started to lower the helmet onto her head.
Right before the spirit placed the helmet on Luna's head, Princess Celestia was walking nearby, as she couldn't find Luna inside the maze. "Where could she be?" Celestia thought to herself. But then, suddenly, Celestia heard what sounded like a small explosion nearby, and when she looked, she saw a large cloud of blue smoke emanating from behind the very bush that, unbeknownst to her, Luna and the spirit were behind. Celestia proceeded to cautiously walk towards the blue smoke cloud that was spreading further around the bush. "Who is there? Is it you, Luna?" she asked. She heard no response, but she did hear the sound of hoofsteps coming from inside the smoke cloud.
As Celestia got closer, she could make out the silhouette of somepony walking out from behind the bush. She did not think it to be Luna at first, because this pony was much bigger and taller than Luna was, but then she heard the figure speak, "Princess Luna is no more, Celestia. From this day forward, I am—" Luna then quickly flapped her powerful wings to blow away the smoke, revealing herself fully, "—Nightmare Moon!" Nightmare Moon reared up on her hind legs, showing Celestia her frightening new form.