Nightmare Over Equestria Part 4

   Celestia was shocked beyond belief at seeing what her sister had turned into. "Luna!! What in Equestria has happened to you??"
   "I am not Luna anymore, Celestia! And I am not your sister anymore, either!"
   Celestia looked like her heart had just been ripped in two after hearing those words, "Luna…how could you say something like that to us? We've always tried to be a good sister and friend to you our whole lives together...and now you turn against us? Why??"
   "You think just because you're my older sister means your word goes above mine? That everything always has to go your way, and never mine for even one day?? Well, not anymore!!" Before Celestia could respond, Nightmare Moon encased herself in her magical night mane and turned into what looked like a free-floating piece of the night sky. Nightmare Moon's night sky form then flew at Celestia, and Celestia quickly flew up in the air to dodge it. Nightmare Moon then turned around and flew after Celestia, who then proceeded to fly away as fast as she could.
   "What are we going to do??" Celestia thought as she fled from Nightmare Moon, "We can't keep avoiding her, but we don't want to fight her either," Celestia then looked up at the night sky, "But if we don't stop her, the sun will never rise again, and Equestria...no, the whole world will never be able survive without the sun," Celestia knew that she had no choice but to stop Nightmare Moon in order to save the world from utter despair. Celestia quickly turned around, faced Nightmare Moon, and said, "This ends now, Luna!!" She then blasted a magic beam at Nightmare Moon, which struck her and forced her out of her night sky form.
   Nightmare Moon started falling towards the ground, but used her wings to stop herself and get airborne again. "So, you finally decide to fight me, Celestia? Well, don't think you can win! I have more power than you ever had!" Nightmare Moon then uses the power of the Night Helmet and Moon Plate to create a "night energy field" around herself, powered by the night itself. "Let us see you defeat me now, Celestia!"
   "We will do whatever it takes to stop you!" Celestia then used her power to encase herself in an energy field made from the light of the sun. "You are not the only pony who has power, Luna!"
   Nightmare Moon laughed at Celestia. "You really think you can defeat me with that? Mine is powered by the moon and night, which are the dominant forces in the sky now, so my power is increased exponentially!"
   "We will defeat you, Luna. Our willpower to protect our land is strong enough to give us the power to defeat anypony; even you!"
   "Well, we'll just see about that!!" Nightmare Moon then charged at Celestia at full force, and Celestia did the same, with the two colliding into each other. Both seemed to be equally matched, as ramming each other didn't hurt either of them, but neither one would give up. Celestia and Nightmare Moon continued to chase each other down, ramming into one another to try and knock each other out of the sky. Ponies below watched them fight; completely dumbfounded to see Celestia fight this dangerous alicorn whom none of them thought they had seen before.
   After quite a bit of fighting, Celestia's power started to weaken. Nightmare Moon could see this, "Ahh, not so powerful at the moment, I see?"
   Celestia was a bit out of breath. "We will not stop...until you are defeated, Luna..."
   "Well then, let's just see how much strength you have left!" Nightmare Moon then rushed at Celestia with full speed. Celestia, though weakened, rushed at Nightmare Moon as well. The two collided, but Nightmare Moon's power was far too great this time, so she broke through Celestia's energy field and rammed into her. The ponies below watched in horror at seeing their princess become overpowered by this great threat. Nightmare Moon kept pushing towards Celestia with her energy field, but then she instantly stopped herself, the force of the stop sending Celestia flying towards the castle, smashing through another one of the windows in the throne room, and then crashing onto the throne room floor. Nightmare Moon dissipated her energy field, and then shouted to all the ponies watching, "See how your beloved princess is no match for the likes of me?"
   "Who are you??" one of the ponies asked in a frightened tone.
   "Who am I? I am the ruler of the night! The bringer of the darkness! The most powerful pony in the world! I...am Nightmare Moon!" she unleashed a powerful flash of black and blue light from behind her when she announced her name. "And I am here to shroud Equestria in eternal night! No longer shall the sun do away with the night sky with its accursed illumination! And nopony, not even your princess will ever be able to take away the night again!!" Nightmare Moon started to laugh evilly, as all the ponies below were truly horrified at the thought of the sun being gone forever.
   Celestia pulled herself up off the floor in the throne room. She looked out the broken window and saw Nightmare Moon frightening all of the ponies with her display of her magic powers. "She's gotten to powerful...I...I can't beat her magic with mine..." Celestia was so distraught, she has even forgot about using the royal Canterlot voice. "There's...only one way...I could possibly defeat her..." Celestia lowered her head and shut her eyes. "Even though I may never forgive myself for doing it..." Celestia then ran out of the throne room as fast as she could.