The Lord of Chaos watched that scene through one of his mirrors and he couldn’t be happier.
“Yes!” he exclaimed. “Finally she snapped. And now Celestia is the only obstacle remaining. Once she is out of picture, the Pony Reality will be submerged in an eternal darkness.”
And he laughed.
Once Luna stopped laughing, she looked angrily to Celestia, firing then a beam that hit a statue and then moved it up to the ceiling, causing it to collapse. Celestia dodge easily the debris by taking flight and watched as Luna walked through the smoke. The latter launched another beam to Celestia who dodged it, creating another hole that let the moonlight get in. The princess of the sun landed and then said:
“Luna, I will not fight you! You must lower the moon! It is your duty!”
“Luna?” her sister replied. “I am… Nightmare Moon!”
Celestia couldn’t believe what was happening. The way Luna, or rather Nightmare Moon, was talking was similar to Ingrid when she became the Snow Queen. But Celestia was determined to not let the same thing happening.
“I have but one royal duty now: to destroy you!” Nightmare Moon exclaimed, casting another magic beam.
Celestia dodged, taking flight and flying away by getting out through the big hole at the ceiling.
“And where do you think you're going?” Nightmare Moon asked, taking flight as well to follow her.
Nightmare Moon went after Celestia, firing magic beams at her, only for the princess of the sun to dodge, while trying to escape. The continuing firing of Nightmare Moon started to cause some damages to the castle, but it was then that Celestia was hit, releasing a moan of pain and falling into the throne room through the hole. Before that, Nightmare Moon laughed and then moved away, going in direction of the party.
Celestia, despite the nasty hit and fall, was able to get up. However, she could feel her heart broken, as she had lost the only sister she still had. It was just like how it happened with Ingrid. Now what could she do to save her?
“I can hear your call for help, my child” a voice said.
Celestia looked up and saw the Lord of Order.
“My Lord!” she exclaimed. “It’s so good that you’re here. My sister, Luna, she…”
“I know, but, as you may know, I can’t interfere in the affairs of ponies” the Lord of Order replied.
“But I need to save Luna” Celestia said. “She has to hear the voice of reason.”
“Your love for your sister is commendable, Celestia, but just like you did with Ingrid, you have to think of your subjects first” the Lord of Order told.
“But…”
“Your sister’s heart, right now, is consumed by darkness. My brother planned each course of action, starting with Sombra and then Oogie Boogie. They both made her vulnerable to her jealousy and I’m afraid right now you don’t have the power to bring her back.”
“But there must be a way” Celestia said.
“The only thing you can do is this” the Lord of Order said, pointing his spear.
A mechanism opened on the floor and so the same device that had the Elements of Harmony at the cave came out, with each element in its rightful place with the Element of Magic inside the stone sphere. Realizing what the Lord of Order wanted her to do, Celestia reacted in the only way she could:
“No… No, I can’t do that! I can’t trap my sister using the elements. It would make her be like Discord and Sombra. I know I can still reach her and I will prove it.”
Having said that, she took flight, following her sister. The Lord of Order watched her for a few seconds before disappearing.
At the party, Orion was a little worried because of the way Celestia had teleported away. Noticing his look, Rose Quartz approached him and asked:
“Are you okay, Orion?”
“I don’t know…” he said. “Something is happening. The fact the moon didn’t low and how Celestia went away without saying anything… I just have a bad feeling about this.”
It was then that screams were heard, with hooves pointing to the sky. Orion and Rose Quartz looked at the sky and couldn’t believe what they were seeing. Nightmare Moon was hovering at the sky, looking down to her subjects with a wicked smile. Using her Royal Voice, she declared:
“Greetings, my dear subjects. Listen well, because I have announcement to all of you. From this day on, the night will last… forever!”
And she unleashed a wicked smile, while her misty mane extended and flowed and thunder was heard. Ponies started to tremble in fear. Moving to face her sister, Orion asked:
“Luna, what are you doing?”
“I’ll tell you what I said to that despicable sun princess of yours” Nightmare Moon replied. “I’m not Luna, but Nightmare Moon. And I will impose the eternal night to all of you. And the ones who dare to defy me will pay with their nightmares.”
In order to make an example to everypony, Nightmare Moon charged her horn and created a pulse of magic that hit everyone there. All the ponies started to be invaded mentally by their worst nightmares. It was just like when they were sleeping, excepting the nightmares were more vivid and the ponies couldn’t escape them.
“Don’t worry, the nightmares will pass, as soon you recognize me as your sole princess and start adoring my night” Nightmare Moon said to the ponies.
“Luna!” a voice called.
Celestia appeared, hovering a few hooves away from Nightmare Moon. Indifferent to her presence, the latter said:
“So, I see you still have the courage to defy me. Pity… I was hoping you would be reasonable and run when I gave you that chance.”
“This has to stop, Luna” Celestia said. “I know that is not you. You can’t be this thing you’re showing.”
“You can bet I am, sister” Nightmare Moon replied. “And I have to thank you for that. You made all our subjects to love your dear precious light and despise my beautiful dark sky. It was all that what allowed me to become who I am now.”
“That’s not true” Celestia said. “Nopony despises your night, Luna, and I did everything I could to make sure both our rules in this world were celebrated.”
“Enough with your lies” Nightmare Moon told. “It’s time to end this… once and for all!”
Having said that, Nightmare Moon fired another beam to Celestia. She dodged and continued to do the same with her sister’s next attacks. However, it came to a moment Celestia couldn’t hold herself any longer.
The two sisters started to shock against each other while charged with their respective magic, while attacking each other physically with each contact. Nightmare Moon was the one with the most ferocious attacks, causing Celestia to defend herself.
It was then that the two sisters casted against each other with beams, starting to measure strengths. With tears at her eyes, Celestia gave everything she had to defeat Nightmare Moon so she could get her sister back, but the villainess’ hate was so great that allowed her to overcome Celestia’s attack and hit her.
The explosion casted Celestia against the castle, falling in the throne room and hitting the structure where the elements were. The shock caused the Element of Magic to get out of the stone sphere and fall beside Celestia, who noticed it. She then saw Nightmare Moon to head towards her, while breaking through a window grass.
In an act of impulse and with more tears on her eyes, Celestia hold the Element of Magic and channeled its magic along with the power of the other five and that created a powerful wave that hit Nightmare Moon and launched her away, while making the most powerful element disappear. Nightmare Moon then disappeared and the image of a mare appeared on the moon. She had been sealed in the same thing she used to raise to bring the calmness and tranquility.
Horrified by what she had done, Celestia was overcome with pain and grief and screamed:
“LUNA!”
With the disappearance of Nightmare Moon, everypony that had been put under her influence had been released. Despite her actions had freed everypony, Celestia couldn’t feel good in any way. She had lost her two dearest sisters, the same ones she used to play and laugh with. Their lives used to be so simple and pure, but everything changed for the worse. She saw them turning into villains and being defeated, one trapped in a urn in Tartarus, while the other was sealed in the moon.
A hand was placed on her shoulder and Celestia knew by the presence to whom that hand belonged.
“Why it had to be this way?” Celestia asked.
“Because if you hadn’t done that, Equestria and all the Pony Reality would suffer” the Lord of Order said.
“Yes, but saving this reality had a terrible cost” Celestia said, while raising up. “Not only I lost the Element of Magic, but I’ve lost the only sister I had… and it was all my fault.”
“You may have suffer a great lost, but you haven’t lose everything” the Lord of Order said. “You still have your brother and this kingdom.”
“What’s the meaning of that without having Ingrid or Luna to share with?” Celestia asked.
There was a silence and then the Lord of Order said:
“Celestia, do you know why the day was meant for ponies to play and laugh, while the night was meant for them to sleep and dream? It has a more profound meaning than just because of balance. It’s because the shiny light of the day allows them to be happy, while the soft shade of the moon gives them tranquility and safety. You can’t responsible yourself for the actions of your sister. She made her choice… Perhaps manipulated by my brother’s minions, but she made her choice. And I hope you also make yours, Celestia, one that is right and not selfish.”
Those words from the Lord of Order really affected Celestia. Despite the sadness she was feeling, she knew he was right. She shouldn’t carry the weight of all the guilt she was feeling.
“You’re right, my lord” she said. “And that’s exactly what I’m going to do.”
The Lord of Order nodded and said:
“That’s the Celestia I know. And as a reward for that resolution of yours, I will share you a prophecy.”
“A prophecy?”
“The power of the elements won’t last forever” the Lord of Order said. “Eventually, it will wear off.”
“You mean…” Celestia started. “You mean Luna will return.”
“Yes, and she will still be Nightmare Moon” the Lord of Order replied. “And everything will happen on the longest day of the thousandth year. The stars will aid in her escape, and she will bring about nighttime eternal.”
“But how can I stop her if I don’t have the elements?” Celestia asked. “She’s too powerful to me to handle.”
“The magic of the Elements of Harmony will be revealed to you” the Lord of Order told. “You will know when the light of the sixth element appears. When that happens, you will groom that light and join it with the rest of the others. Don’t worry, this will make sense to you once that day arrives. Now, Celestia, I believe it’s time to raise your sun for the longest day.”
“But, without Luna, how will the night and the moon be raised?” Celestia asked.
The Lord of Order didn’t reply right away, only tipping his finger at the tip of Celestia’s horn that glowed momentarily with the same aura as Luna’s.
“From now on, until the return of your sister… your real sister Luna, you’ll be responsible for both the sun and the moon” he declared. “I just hope you’re up to my expectations.”
“Don’t worry, I will” Celestia replied.
The Creator nodded to her and disappeared in a burst of light.
Celestia looked to the moon and the mare on it.
“Don’t worry, Luna. One day, we will be together again, little sister.”
And so, she started to sing a song. It was a lullaby for her little sister, where she showed the remorse she was feeling and how she regretted not being able to help her. The lullaby also had the hope she had of being reunited with her, adding how those thousand winters would pass slow to her.
Celestia wished a good night sleep to Luna, before lowing the moon and raising the sun, initiating a new day…