Doctor Hooves and his companions had returned to camp while Nightmare Moon panicked about the Elements of Harmony, from what the demonic Alicorn said it was obvious that Celestia was here. It was close enough to nature to see it die and she had a bed to sleep in. It was the perfect way to torment her.
She was crying when they found her. All of the Elements of Harmony were around her neck just as they had suspected, she had what she needed to defeat Nightmare Moon but as Doctor Hooves mentioned it she just shook her head and wept. "How could I? She's my sister!" Celestia cried out to the alien doctor. But he knew she would have to.
"If you don't do this then all of the world will pay for it." Doctor Hooves said bluntly "The plants will die, then the vegetarians will die and then finally the carnivores will die. That will be on you Celestia."
All the princess did was continue to shake her head and weep. They would have to try and convince her.
***
It had been two days, well that was what they assumed and some of the smaller plants had begun to wilt. Celestia spent her days pacing, contemplating, thinking. She spent her nights crying herself to sleep as the realisation began to dawn on her as to exactly what she would have to do in order to keep the entire world safe but she also knew that she would never be able to do it, her courage would fail her as she had no idea if Luna would survive the process or not.
The travellers were having trouble getting to sleep again, I'm not even tired Sugar thought are we sure it's that late?. Big Mac and Cheerilee lay awake, silently wishing they could just go home but they knew that Doctor Hooves would not leave until he had seen Equestria saved. They started to worry if he was going to get them killed.
Doctor Hooves himself had spent the last two days trying to convince Celestia that she must use the Elements of Harmony and that when the time came she would have the strength to use them. She had thanked him every time for his confidence in her but thought it was misplaced. He was beginning to wonder if he should just leave her to figure things out for herself. No he thought as he lay in bed get that crap out of your head because she definitely needs your help, he hated the thought of running from something this important and was ashamed for it to have even crossed his mind.
It was a problem that wasn't going away any time soon.
***
A week after the rise of Nightmare Moon and the small plants were all but dead, they had spread their seeds but it was quite obvious that without the sun these new plants would never grow to replace the old ones. Celestia was pacing again, they hated seeing her like this and were counting on Doctor Hooves to do something. He had been trying and trying all week but she wasn't listening, but he was willing to try again.
"Princess," he said as she was pacing "I know this must be hard to accept but that creature isn't your sister any more. It is your duty to safeguard Equestria against these threats and you must do so. I am truly sorry but it is a cold truth that must be accepted here and now before every creature dies a slow death by starvation. I know your..."
"You're right"
Doctor Hooves stopped his speech immediately and listened to the rough voice the princess had gained during her long nights weeping.
"While I still believe my sister can be saved I have a duty to my people I must fullfill. Very well Doctor, I will use the Elements of Harmony but first answer me this and please do not lie. Will this kill Luna? Seeing as you're from the future you should be capable of answering."
Doctor Hooves smiled at her "The elements will not kill her, she will be out of the way for quite some time though. And, if I might add, without these events coming into play the future will be forever lost. Six of the most significant ponies to ever exist will never be born and that will cause a paradox that could potentially end all life in the universe. No pressure."
Celestia giggled at that last part, a sad, dry giggle. "Then we should be going then. You four accompany me to Canterlot, it's time we had a chat with my sister."
***
They trotted through Canterlot with a purpose, Celestia had a stern look on her face but the red around her eyes clearly showed everypony they passed that she had been crying. They moved closer and closer to the centre of the city, abandoned guard armour became more common as they got closer to the castle. Celestia couldn't blame the guards, they just didn't have it in them to fight against the princess it had once been their job to protect.
They turned the corner to the palace and saw that Nightmare Moon had been standing outside the castle. She had clearly been expecting them to attempt to save everypony from her eternal night, she could not allow that to happen.
Nightmare Moon let out a chuckle "Well, well, well. I was wondering what had taken you so long," she said "when the Elements of Harmony vanished I thought you would have been back here immediately. Apparently you're not as strong willed as I once thought you were and that, my dear sister, is why the Elements of Harmony will not hurt me while in your possession." The black Alicorn's wings began to flap as she took to the air "Come now. Let us end this!"
Celestia's horn began to glow, as did Nightmare Moon's. Celestia's horn glowed a bright blue while her evil sister's glowed a dark purple. Doctor Hooves immediately noticed that Celestia was not using the Elements of Harmony. She was still holding back.
A beam of dark magic erupted from Nightmare Moon's horn and met with the beam of blue that Celestia's horn had now produced, At first Nightmare Moon's was pushed back but as she steadied herself in the air it became clear who's magic was stronger now as the beam of purple energy began to close the distance between it and Celestia.
"Princess," Doctor Hooves began "you must use the Elements of Harmony now!"
"Not... if there's even... the slightest chance... of saving... Luna." Celestia said intensely, this battle was clearly taking its tole on her.
"She'll kill you before you get the chance and even if she doesn't, you're liable to kill her if you keep this up!"
Celestia looked at him for a moment and saw that he was right, she would have to use the elements or risk the life of her sister. She closed her eyes and concentrated, never letting her magic down.
Nightmare Moon laughed maniacally "Fools, do you really think she was the will to use those things against her sister? I'll kill her because she is weak and there is nothing anypony can do about it!"
The Elements of Harmony began to glow, brighter than the horn of any Unicorn or even any Alicorn's horn. Nightmare Moon froze with horror, the elements are working, how are the elements working for this weak willed pathetic waste of Alicorn flesh. She let her beam of magic down and felt a surge of pain all over as Celestia's still active beam of magic smacked her out of the air.
The grounded black Alicorn was now terrified, what was Celestia going to do with the elements?
Celestia's voice went into the Royal Canterlot Tone "Nightmare Moon, you are hereby accused of attempting to use the moon to plunge Equestria into eternal night. You are found guilty and sentenced to life on the moon you hold so dear. Prepare yourself."
The power of the elements left them and found a new home in Celestia's horn, she then opened her eyes and a rainbow coloured beam of powerful magic shot out towards Nightmare Moon at lightening speed. Nightmare Moon struggled with the power of the magic and began screaming, begging for mercy. The rainbow closed around her and then flew up into the night sky, carrying her with it.
The crowd of bystanders that had gathered by this point looked in awe up at the sky as a shape appeared on the moon. The dark shape of an Alicorn's face stared down at them from where Nightmare Moon was now imprisoned.
Celestia thought the time was about right and her horn began to glow once again, the moon began to lower. The evil Alicorn's face disappeared over the horizon and where they saw it go down the great ball of fire that is the sun began to rise in its place.
Cheers went out from the crowd as the sun once again took its place in the sky, Celestia's horn stopped glowing and she turned her head towards the time travellers and smiled for the first time in seven days.