It was Zerus. With his eyes closed, the young purple colt slowly drifted down in front of the bowing Tirek, growing quickly a moment later into a strapping young stallion, his coat turning gray as his long brown mane was tied back and draped down his shoulder. As the crowd watched, the Alicorn Amulet slowly drifted toward him and fastened itself around his neck. Finally, he opened his gleaming red eyes and looked down at his servant.
“Thank you Tirek.” he said in a youthful voice, Twilight immediately noticing it as the voice she had been hearing as of late. “You have served my father and I well over the last few centuries.”
“Yes, Master Zerus.” Tirek said, still bowing to his lord. “It is a shame that Grand Master Sombra could not be here for this moment-”
“Rest assured.” Zerus interjected. “My father's dream will be fulfilled. Cataclysm awaits.”
“Yes, master.” Tirek said, still kneeling before the young stallion. “Grand Master Sombra would be so proud of you... this is your defining moment-”
“No, Tirek.” Zerus said, a small smile on his face as he looked down at his subject, placing his hoof gently onto his shoulder. “This is our defining moment... our destiny.”
Looking up at the awestruck ponies, Zerus slowly stepped past Tirek, who slowly rose to his cloven hooves.
“Greetings everypony.” he said calmly, Tirek fastening a pure white cloak around his master's shoulders. “I am Zerus... pupil of the great king Sombra.”
“Zerus...” Luna said, her eyes quivering as she stepped toward him. “How... how are you...”
“I suppose I do owe an explanation to the princess.” Zerus said solemnly, nopony speaking as he stepped before them. “When I was trapped inside the Crystal Empire, I wandered the streets for many days, slowly losing myself as the crystal ponies tended mindlessly to their faded town. Neither I nor they could leave the boarders, the sun nor moon never moved, the wind never blew... it was enough to drive anypony to madness... but then, when I was inches from giving up... I heard a voice... a voice I had been taught to fear.”
“Sombra...” Twilight said slowly, Zerus nodding.
“Initially... I did fear him... but his words were always comforting. He always spoke kindly to me, always pitied my fate, despite his own, sealed away inside the endless darkness of Cataclysm by the Elements of Harmony... and he then began to teach me magics... magics far greater than anything I could have ever hoped to learn under the tutelage of Starswirl of the alicorns.” he said, both Celestia and Luna feeling their hearts grow heavy as he spoke.
“He became more than a mentor to me at the Crystal Empire... he become a father... and I vowed to find a way to help him escape... an instrument of pure energy.”
“You created the Alicorn Amulet?” Luna breathed, Zerus nodding slowly.
“I tried to break the seal the Elements of Harmony had placed on my father and free him from the void of Cataclysm... but my magic was still untempered... and I found myself in the void with him.” he said, the two alicorns' eyes growing wide at this. “In the void, however, he and I were able to do so much more together... we were able to better each other, teach the other more magics and grow stronger in the endless hatred and fear that swirled around us infinitely... and ultimately, we managed to force the Alicorn Amulet I brought with me into the void back into the world, and not in the sealed empire.”
Celestia and Luna couldn't believe their ears. Zerus had done all this with Sombra?
“The amulet traveled from one being to the next, and we awaited the one whom would wear it long enough... long enough that they would be able to commune with my father and me... but all who wore it died... save one.”
“Tirek.” Shining Armor growled, Tirek nodding.
“I was not only the only one to wear it long enough to form a bond to both Cataclysm and Master Zerus and Grand Master Sombra... I was also the only one to be fooled into taking the amulet off, same for Trixie eons later... it was my chronicle of the amulet you found, Celestia.” he sneered, her eyes going wide as she remembered their encounter at Starswirl's tower. “Why would I be after that information, you wonder?”
“To keep us in confusion when you really knew everything that was going on...” Celestia stammered.
“Then,” Zerus continued “the unthinkable happened... the seal of the Crystal Empire broke and my father began to slowly slip back into the world... he and Tirek vowed to find the amulet so that they could free me... but then... he was killed... by the Crystal Heart.” Zerus said sorrowfully.
“By the time I had reached the Crystal Empire, Grand Master Sombra was long dead.” Tirek said, looking over the red horn in his hand.
“My heart ached.” Zerus said slowly. “My father was dead... and so it was up to us to enact his glorious plan for the world... we who had bonded with it would unleash it... Cataclysm.”
Nopony dared speak a word, save one.
“What is Cataclysm?” Twilight demanded, stepping forward, everypony shuddering at her bravery.
“Cataclysm” Tirek began “is a malevolent force of hatred and fear forged by Starswirl and the baphotaur mystic Lock-Nah during a war that raged millenia ago.” Closing his eyes, Tirek smiled wickedly. “When it threatened the land, they ended the war so as to seal it away forever, as they could not destroy it... yet.”
“By the time the Elements of Harmony were all born into this world, Cataclysm was long since sealed away.” Zerus explained. “My father learned of it and what it could do to the world... it has the power to rend asunder the entire world, destroy everything in existence... and then life will begin anew. A world nopony has ever seen before.”
“Zerus, please, don't do this!” cried Luna, stepping forward, her face wet with tears. Zerus slowly walked toward her.
“Princess Luna.” he said in a respectful tone, walking up to her. “I thank you for how kind you were to me.” he said, slowly lowering his head to hers. The moment their horns touched, however, she was sent flying at blinding speed, crashing int the castle wall and left lying motionless on the ground as she shrunk to a tiny filly, everypony looking on in absolute terror at his power.
“I did not explain myself to you, Princess Luna.” Zerus said, turning to the newest alicorn. “I explained myself to you, Princess Twilight Sparkle.” he said, Twilight feeling her blood run cold. “Come with me, Twilight. It's what I want.”
Twilight stared at him as Tirek bowed to her, nopony speaking a word.
“No.” she said. “I will not come with you.” Zerus made no movement, though Tirek rose quickly, scowling at the young princess.
“I won't let you harm anypony... and I won't let you kill everything!” she said sharply, surprised by her own bravery. “I'll never help you.”
“I understand.” Zerus said calmly. “You're just young, naive, ignorant of the way the world truly is... like I was so many eons ago.” he said, Twilight getting a cold chill. “I will not be denied, however.” he said, powering his horn, Twilight buckling to her knees, her eyes turning green as purple flames danced from her eyes.
“You gave into hatred at the Crystal Empire, and I can still feel it coursing through your heart and soul.” he said, coming closer. “Why do you fight it-”
“I'll never... drop to... Sombra's level-”
“You watch your tongue!” Tirek snapped, Zerus only waving him off.
“Let it go, Tirek... I have ways of persuasion.” Zerus said, levitating Sombra's red horn and placing it on Twilight's Element. Immediately, she felt her body go numb, her consciousness fading fast.
“Let this remind you, Princess Twilight Sparkle,” Zerus said coldly “why you once feared the dark.”
“Twilight!” Celestia called, the purple alicorn stumbling toward her mentor, black crystal growing up around her Element.
“Help me, princess,” Twilight whispered, tears streaming down her face “I've never been so afraid in my life...”
"Go, Princess Twilight Sparkle,” Zerus said proudly “like a vector to the heavens, go!”
Immediately, Twilight spread her wings, flapping up a massive gust that Celestia walked through easily. When this proved to be ineffective, Twilight rushed silently for Celestia, swinging her sharp horn for the white alicorn, Celestia countering.
“Twilight, please, don't do this!” Celestia cried, a lazy look on Twilight's face as she slowly pushed her mentor back, her eyes still alight with the power of hatred. It seemed as if her actions were not her own. Turning, Twilight kicked Celestia high into the sky and shot for her, the two firing on each other.
“Twilight, no!” Shining Armor called, racing for the dueling alicorns, Cadence by his side as they charged, Tirek snatching them both up by their throats in a flash, holding them high as they kicked and struggled helplessly, the others looking in terror.
“Discord, if you please.” Zerus said, stepping toward the two captured ponies. “You will all surrender your Elements of Harmony.” he said calmly, his glowing horn pointing right for Shining Armor and Cadence as they struggled on. “Discord, collect them for me, please.” he said, Discord glaring at the two, Twilight and Celestia battling in the Canterlot sky. “I said collect them for me.” Zerus reiterated calmly, stepping closer to the two, his horn inches from Shining Armor's belly. Immediately, Rainbow Dash tore her Element from her neck and threw it as Zerus' feet, the dark unicorn looking it over.
“It would seem somepony wants them to live.” he said, his smile curling. “The rest of them, please.” he said, Discord walking to the rest of them, each of them sorrowfully removing their Elements and giving them to him. “Bring them to me.” Zerus said calmly, his horn still glowing. Growling, Discord stepped to the wicked stallion and held the golden necklaces for him. Powering his horn, Zerus levitated all five of the stolen Elements of Harmony and started off toward the shatter podium.
“We leave, Tirek. Let them live.” Instantly, Tirek dropped the two and started for his master, Shining Armor and Cadence both coughing and wheezing. As the ponies hurried for Twilight's kin, Discord gave the two a murderous glare as Tirek seized Zerus and spread his bat-like wings, flying off into the twisting storm that had gathered around the land. They were powerless without the Elements of Harmony.
Twilight zoomed for her teacher, firing a deadly blast of energy, Celestia barely shielding herself with her magic. Wasting no time, still with a half-awake look on her face, Twilight fired again and again for Celestia, each blast aimed for a vital spot on her body. Twilight would kill her if she got the chance, Celestia thought as she felt her blood run cold. Shooting for Twilight, Celestia smacked her pupil hard in the face with her wing, Twilight spiraling to the ground.
“Twilight!” Celestia called, flying for her. As she closed in on her tainted pupil, she saw the purple alicorn curve back into the sky and fire for her, Celestia barely managing to shield herself. Twilight then shot straight for Celestia and began to savagely kick and thrash at the barrier. As her horn glowed brighter, Celestia's barrier grew enormous, knocking the vicious pony away. Dropping her shield, Celestia shot for Twilight, her horn growing sharp and the two crossed horns.
“Please, Twilight!” Celestia called. “You cannot allow yourself to be taken over.” Twilight's face made no expression. “Resits the powers of wickedness! You must-” Celestia stated before Twilight dropped below her, letting her flip through the sky as she tried to regain her balance, her wings flapping in a frenzy. Before she could round back into the fight, though, she felt a sharp pain shoot through her back as Twilight fired on her, making a direct hit on her spine. Celestia fell through the sky, Twilight still firing a barrage at her, striking her each time as she fell into the moat with a loud splash. Celestia waited there, holding her breath, the dead stallion that attacked her before floating behind her. She could tell Twilight was not attacking with her full power... was she holding back? If so, then why were none of Celestia's words getting through to her. She had to think of something, though. She couldn't allow Twilight to leave for wherever Zerus and Tirek had gone, or even worse, to attack Canterlot. Exhaling, Shooting to the sky, Celestia knew it was time for her to stop holding back
Flying up before Twilight, the two of them staring the other in the face, Celestia bowed her head, tears dropping down her cheeks. The two shot higher and higher, into the stormy clouds and far out of view of the marveling crowd.
“Forgive me, Twilight.” she said as she suddenly came to a stop and fired a gigantic blast for Twilight, the young princess countering with her own attack. As the two held their torrent of magic in place, Celestia mustered all her strength and shot back with every ounce of magic she had, her beam of glowing energy engulfing Twilight's and encasing around her horn. As Twilight strained with Celestia's assault, Celestia knew she had to end things here by any means necessary. Roaring out, her magic attack growing bigger than ever, Twilight's horn became engulfed with Celestia's magic and exploded.
=====
https://www.youtube.com/watch?v=enWgR3SLDYo
The ponies down below covered their face as a giant burst of light illuminated the blackened sky. As it slowly faded, the denizens of Canterlot slowly opening their eyes once more, they saw Celestia slowly descending far off toward the tiny, unconscious Luna, nuzzling her. It looked like she would be safe at least.
“Princess Celestia!” Rainbow Dash called, hurrying over to Celestia, her friends joining her as they came to the white alicorn. “What... what happened to Twilight?” she asked in a shaky voice. “Did she... did she... die?”
Celestia said nothing and bowed her head as something tiny dropped down out of the sky before them, making a small clanging sound as it came to a rattling halt. Immediately, everypony except for Celestia gasped as they saw what it was. Twilight's diadem, smoking but still covered with black crystal shards. Instantly, Celestia shot into the air, a number of the ponies crying with the loss of their friend.
The world would not be the same without Princess Twilight Sparkle...