“Sister, what in the Equestria is happening?” Luna tried to calm Celestia.
“No time! We need to get out of the Castle!” Celestia bolted to the side and tried to slip past Luna. Luna blocked her sister’s path.
“Whoa! Tell me what is happening first, then we can go,” Luna looked her in the eye.
“Luna! Please! We need to-” She was cut-off midsentence by the farthest wall of the corridor shattering. Green light pierced the cracks of the stone, then faded with a slight hiss. Rumbling could be heard from underneath the debris.
“Mata Nui!” Celestia cursed under her breath. “Change of plans, we need to get to the throne room,” Celestia used her golden magic to levitate Luna in the air.
Luna saw what her sister was talking about. The rubble scattered as an unfamiliar creature emerged from the pile of debris. She couldn't quite see it clearly before Celestia shut the palatial doors of the throne room.
“Celestia, tell me what the hay is going on!”
Celestia, between gasps of air explained to her sister. “That creature you saw, its name is Teridax. He is after the mask left in my hooves for safe keeping.”
“You’re not making a whole lot of sense. Do you mean Tirek? What about a mask?” Luna was just able to finish when another wall burst outward in a green light.
When both Alicorns could see again, the creature entered the throne room.
The creature was grotesque, made up of an unholy mix of organs and mechanical parts. This creature was prominently humanoid, though his form was hunched over. He possessed a set of reptilian wings and his eyes glowed a blood red.
“So, Celestia, end of the line are we?” The creature spoke in a guttural, raspy voice.
“You’re not welcome here, go back to the hole from whence you came,” Celestia retorted. Her horn glowed in the golden light as the creature approached her.
“My, sassy as always, sister,” The creature chuckled.
“SISTER?” Luna was dumbstruck. How was this creature her ‘sibling’.
“I see that you've made quite some progress, last time I entered Equestria,” the Creature glanced at Luna, a devilish grin stretching across his face. “I see that your sister is free from her prison, just like you did to me,”
“I banished you then, I can banish you again,” Celestia’s horn glowed brighter.
“You know that is a lie,” The creature shifted. “Last time, you used the elements to send me back to Metru-Nui. Now, since I have regained my strength, your so called ‘elements of harmony’ cannot affect me,”
He started to pace about, observing the windows of the throne room. He stopped at the stained-glass window where spike saves the crystal empire “I see that you have made progress indeed, I suspect Sombra is free also?”
“Celestia, tell me what is happening!” Luna shouted.
The Creature snickered “You have a lot to learn, little sister.” Luna balked at that comment. The creature gestured to Celestia “Your older sister has been keeping secrets from you,”
Luna shifted her gaze over to Celestia, eyes full of concern. “Is he telling the truth? Have you been keeping secrets from me?”
“Luna, don’t listen to him, Teridax only wants to syphon your powers,” Celestia had her eyes full of tears.
It was happening again. The evil was back, trying to steal Luna for another thousand years.
“Please! I don’t know what is going on!” Luna pleaded.
Celestia shook her head in disappointment. Sighing, she began, “I was entrusted with a mask from one of my best friends, Mata Nui. I've only mentioned the name a couple of times. Long story short, Teridax is here to steal that mask.”
“Smart Pony!” Teridax clasped his hands together. “Yes, that is what I am here for. So, I’ll make this easy, give me the mask, and I’ll leave your little nation alone for a millennium.” Teridax offered.
Celestia stomped her hoof and grunted. “Never! It is my duty to protect Mata Nui’s mask!”
“Ooh, feisty!” Teridax smiled devilishly. “So you want to play it that way. Whatever, it's your choice”
“You can have the mask when you pry it from my cold-dead corpse!” Celestia shouted.
Luna didn’t think Celestia would go as far as death to protect something. Then again, she protected the elements of harmony before Discord snatched them.
Teridax started to approach Luna. “No, I think I have a better idea,”
A barbaric staff materialized out of the air and landed into Teridax’s hands. He lowered the staff, lining the sights toward Luna. A red aura shot out of the tip.
Luna knew what Teridax was doing and tried to dodge the blast, but the red aura ensnared her. Luna quaked uncontrollably as the red aura paralyzed her being. She tried to use a teleportation spell to escape it, only to find the aura extinguished her magic.
The red aura intensified and started to inflict pain all over her body. Teridax grinned at the sight of Luna being tortured.
“Wait!” Celestia halted Teridax. Celestia called upon her magic and teleported a golden mask near her. It had the inscription of a humanoid figure in front of it, but nothing else.
Celestia held the mask in her magic, presenting it to Teridax as bait.
“Good pony, now give it to me, and you nation will be spared” Teridax instructed. The red aura wore off as the giant approached the sun goddess. Celestia pulled the mask back, closer to her face when Teridax got close.
“You are a fool Celestia. You put on that mask, you will give up all your powers, and your whole life of being an Alicorn is wiped clean,” Teridax inched closed, each of his footsteps shaking the floor.
“…A worthy sacrifice, one that I’m willing to make” Celestia took a deep breath “In the name of the ponies of Equestria, and Mata Nui, I accept this mask as the necessary sacrifice for my nation to live!” With a click the mask was secured to the Alicorn’s face. Celestia’s horn glowed bright gold as the magic spell formed a golden orb around her.
The final flicker of light goes out as the resounding shock-wave knocked Teridax out of the Castle equal to Queen Chrysalis. He screams as the magic propels him outward, farther than the badlands of Equestria.
Luna rushed to Celestia’s side right as the light was about to go out.
“Take care of the sun while I’m gone,” Celestia’s voice was distorted, changing to the point… where it wasn't Celestia anymore.
“I… I will,” Luna managed to say.
Suddenly, when the transformation was done, Luna opened her eyes. She was greeted by an odd looking filly with cybernetic parts aside her legs, hooves, and body. The mask occupied the filly’s beautiful face. The filly was like young Celestia: white coat, pink mane, down to the detail where there wasn't a cutie mark yet.
Suddenly, the Filly woke up. The pink eyes she knew and loved.
Luna took it all in. This wasn't her sister anymore. This wasn't Celestia.