//------------------------------//
// Chapter 7 
// Story: An Old Mare's Tale 
// by realbrickwall 
//------------------------------//

Princess Celestia followed the tug of her horn as she honed in on the energy signature of Luna's spells. The tracker spell wasn't usually worth trying, as it couldn't distinguish between different spells, but there was no other choice. Celestia could feel that her little sister was in danger, with a magic much deeper than that channeled through her horn. There was no time to lose.
Eventually, she located the closest location. A stall in one of the town squares in the lower quarter. The princess beat her wings faster and crashed into the door, where she found herself face to face with a blue unicorn with glittering hair.
"Welcome to Shimmerstar glassworks. I'm Shimmerdust, the-" the smiling unicorn began before Celestia cut her off.
"Have you seen Princess Luna?" The princess tried to sound calm, but she was breathing heavily, and her expression of concern was unconcealable.
"Why, yes, she came in here-"
"Which way did she go?"
"Back to the palace." The unicorn seemed completely unperturbed.
"I just came from the palace, of course she's not there!"
"Why, whatever were you doing at the palace?" The unicorn tilted her head. "Sayy…you're the princess, aren't you?" Celestia looked back to make sure her wings hadn't fallen off. Why would anypony even ask that?
"You must be the Shimmerdust I've heard so much about." She sighed.
"How do you know who I am?" the unicorn asked with wide eyes.
"You told me your name ten seconds ago."
"I meant how have you heard about me? Of course I know I told you my name. I'm no airhead." Celestia's eye twitched.
"Look, my sister is missing, and my tracker spell led me here. Do you know why?"
"Sure. My boyfriend said she teleported in here when she came in earlier today. But if it's magical auras you're looking for…" Shimmerdust used her mouth to pull down on a lever that lifted up a large lens, which had, through its light-bending properties, been completely concealing a large pair of glasses behind it. "These show the intensity and properties of magical auras. I've been working on them for over a year now, since I'm not good with magical theory. They were supposed to be a present for…well, somepony else, but I think you need them more." She lifted the pair of glasses onto Celestia's face.
Celestia's eyes were instantly assaulted. The glass shop, already full of color, was now nothing but color. The unicorn in front of her appeared as a vortex of near-white colors and glitter.
"How am I supposed to use these?"
"She teleported in over there," replied Shimmerdust pointing a hoof at a spot on the floor, "so just look at what you see there and try to find the biggest concentration of something similar." Celestia didn't need to focus to see what the unicorn meant. Luna's spell signature was an umbral swirl like a moving painting of the night sky, and quite a bit stronger than anything else in the shop, even the pony.
"Thank you. I'll find some way to repay you." Celestia took off straight up, leaving a hole in the ceiling.
Shimmerdust stood staring up at the new skylight. "I didn't accidentally make those prescription lenses, did I?"

With her new magically enhanced vision, Celestia had no trouble seeing the strongest of Luna's auras. The younger princess had hidden herself deep within the caves under Everfree. Celestia had found a clear spot in town and used her magic to tear through the earth until she reached the caves. She immediately noticed another pony on the opposite side of a still pool of water. The pony was shrouded in darkness, aside from the fading magic around its horn. However, the lenses told Celestia that it was most certainly her sister.
"Luna? Come here, sweetie, and let's talk about this." The other pony didn't respond, or even move. Celestia used her wings to hover above the pool, and inched closer to her sister.
"Why is this happening? What is this?" Celestia heard the sob in the other pony's voice. It was like her sister's, but a bit deeper, and lacking the usual childlike energy.
"Luna, I got mood swings from that spell, too. It's alright. They'll get better, I promise, but right now-"
"Mood swings?" The voice was even deeper now. "Is that all you think this is?" The sob had disappeared. "You still think of me as a witless child, don't you?" The other pony lifted her head. It had the eyes, the horrible eyes, full of evil and the promise of death. "You bitch!"
That's when Celestia noticed that the other pony wasn't so hard to see because of the lighting, but because she was pitch black. On those last words, her mane flared to life, a menacing, living nebula of stars.
"You're not my sister." Celestia looked the other pony straight in the eyes. "What are you?"
"What am I?" The pony chuckled condescendingly. "You can't even spare me the grace of a 'who'? Well, it matters not. Soon, you will be dead, and I will rule Equestria as Nightmare Moon!" The black mare reared up and cast her horn aglow. Celestia's glasses warned her that a lightning spell was brewing, and she threw up a shield just in time to keep from getting electrocuted.
"Give my sister back, you monster." Celestia returned fire with bolts of sunlight. She knew that the evil goddess could easily block them, but they were a simple enough message of deadly intent.
"Oh, Celly, Celly, Celly. I'm still your dear, sweet sister." Nightmare Moon spat the words. "Now come give me a hug!" The mare leapt up to ram its horn straight through Celestia's chest. Celestia pushed with her wings, clearing the height just in time to avoid a goring.
"With pleasure." Before Nightmare Moon landed, the older princess snared her telekinetically and flung her up through the hole that she had made from the surface. Without delay, she rushed up after her to continue the fight. However, on the ground next to the hole, she saw the form of Luna lying on the ground, crumpled up. "No, Luna!"
"Big sister?" moaned Luna weakly. "I'm sorry. I-ARGH!"
With a piercing shriek, Luna's limbs stretched, and her coat blackened, as her hair came to life once again and wrapped Celestia in a stranglehold.
"No," growled Nightmare Moon through clenched teeth, "I won't go back. I won't let myself love you ever again. You don't deserve love. None of you ponies do!" The dark mare threw Celestia to the ground, face-first. Celestia shook the pain away.
"If you really are Luna, then I will always love you. You know that, don't you?"
Nightmare Moon snarled. "You haven't a loving bone in your body. It's all lies. I thought I was the trickster, but I believed your lie for centuries. No! More!" Nightmare Moon kicked Celestia with her front hooves. Celestia felt her breath go, but used the momentum to allow herself an easy liftoff.
"Your mind is being toyed with!" Celestia levitated rocks and hurled them at the dark mare. "Stop this, please."
"No, it is only now that I see clearly." Nightmare Moon easily batted away the oncoming rocks. "You only pretended to love me because you needed me to raise the moon. But you knew you would ascend first, and once that happened, you would-" she was cut off as a boulder from the rear soared past her peripheral vision to hit her solidly in the body. She fell over, and her form slowly started melting back to the form of the young princess.
"I love you Celestia," Luna's voice came through, accompanied by tears. "I love you so much. Please, end it now. She'll-NOOOOO!" Nightmare Moon's full form reasserted itself.
"Oh, but you don't need to know that yet," chuckled the mare of darkness. She flung all the rocks back at Celestia, who had to use both aerial maneuvers and magic to stay safe. Nightmare Moon took off to the sky as well, attempting to engage Celestia in melee combat. Since the dark goddess was bigger than Celestia, she would have the advantage.
"All I need to know is that love will win the day. Perhaps you've forgotten that in Equestria, the heart is the most powerful magic." Celestia climbed into the air, forcing Nightmare Moon to chase her. They reached the level of clouds very quickly, and Celestia landed on top of a large one. Nightmare Moon landed on the cloud as well. From the vantage point, both could see that the sun was low in the sky and painting everything red. "But there's some other powerful magic as well." Celestia's horn glowed, and the red-lit cloud suddenly came alive. It trapped Nightmare Moon's hooves, and her struggles to get free did nothing.
"That sun will go down soon, and then we'll see who has the powerful magic." Celestia paid the words no heed and flung Nightmare Moon to the castle tower, where she crashed through the wall.
"No! She was supposed to resist that." The princess dived after her sister. She stood over the limp form of the dark mare, lying on the floor of the observatory. "Luna! Luna, can you hear me?"
The dark mare's eyes opened slowly. They were the eyes of a pony once more, though none of the rest changed. Tears flowed freely from Luna's eyes, over Nightmare Moon's face.
"Big sis," came Luna's voice just barely above a whisper, "you look totally dorky in glasses."
Luna's shriek of agony resounded through all the lands of the world, marking the Eve of Darkness.

Princess Celestia shook her head to clear the ringing in her ears. She saw Nightmare Moon standing opposite her in the observatory.
"Hm. Finally." The dark mare smiled approvingly at her own hooves. "I was worried that little brat had a fighting chance." Celestia readied her magic for another volley, but Nightmare Moon only chuckled. "Oh, don't worry about that, Celly dear. I was only overreacting because I was a bit at war with myself, you see." She began pacing around Celestia. "Oh, but that was just a phase. I'm all better now, I promise."
"No, Luna, you're not. You need help."
"Luna? Oh, my, it seems you've forgotten." In an instant, Nightmare Moon disappeared into the cloak of her own mane, reappearing right next to Celestia. Celestia hardly had time to register this as she was immediately kicked to the ground. "It's Nightmare Moon now."
"No," groaned Celestia, trying to ignore that some of her ribs had just broken. "You're still Luna. You're still my little sister, and I still love you." She tried to struggle to her feet, but Nightmare Moon kicked her again.
"Of course you do," cooed the dark mare. "Twue wuv always wins the day, doesn't it Cewwy-wewwy." She resumed her pacing. "Well, maybe you haven't noticed, but Luna is no more. I am free of that sickening admiration you programmed into me. But if I loved you, then what was the problem? After all, we all know how magical a pony's heart can be. Oh, I know." She leaned down next to Celestia's face. "Your love just wasn't strong enough." Nightmare Moon walked to the other end of the observatory.
"You're wrong," Celestia said between coughs. "This isn't over. You think that a little injury will stop me?"
"Of course not," snapped Nightmare Moon, "do you think I failed to notice how annoyingly stubborn you can be?" Her mane flared to life, but quickly calmed down. "But it doesn't matter. Your sun will only last another five minutes. Once that happens, they sky is mine. For you see, sister dear," she spat the word, "with my ascension, I've gained the power to control both sun and moon. And the night will last FOREVER!" Nightmare Moon cackled with glee.
"I can still stop you." Celestia struggled to her feet.
"Oh, really? You're running out of time, sister, and the game has changed. You see, beforehand, dear little Luna was holding me back. But now, there is nothing stopping me from destroying you." Celestia felt herself lifted into the air, but not by telekinesis. The magical energy was running through her body. No, it was tearing through it, slowly upwards. "Oh, sister, the heart really is the most powerful magic in Equestria. Now you will see what happens when a heart turns black." The tearing grew faster. Celestia could see the bottom of her body dying and withering.
"I can still stop you," she gasped weakly.
"Have you already resorted to repeating the last coherent thought you could manage? You were always weak, sister, just like all the ponies of Equestria who fear the dark. They will soon learn as you have."
"I can stop everything." Celestia poured all her magic into her horn. It glowed with enough power to bathe the room in light.
"No! You won't get the chance!" Celestia knew that it was obvious what she was doing. She raced to weave the complex magic as the tendrils of death ripped further and further into her body. She felt them reach her heart.
All went black.