Pictures speak 1000 words

Luna finally raised the moon. It was a simple task to do for her, and she was well practiced in it, but the task was made harder by also trying to lower the sun at the same time. She finished wearily, before going back into the castle, where Celestia lay silent and motionless.

Celestia had, for the past few days, neglected her task of raising and lowering the sun. Something was wrong, but she refused to talk about it, even with Luna.

"Tia, what is on thy mind? Thou hast been acting most strangely recently. Thou hast not risen from thy bed nor eaten anything drink in several days, and it troubles us to see thee in such a state." Celestia didn't bother to respond. She merely lay as she had, with her forelegs crossed beneath her chin, her half-open eyes hardly aware of the world.

Luna sat next to her, placing a tender hoof onto her sister's shoulder, unsure whether she should be comforting or stern. "Please, Tia... Tell us how thou canst be aided. We only wish to help thee..."

The chamber doors flew open, slamming into the wall. "Forgive my intrusion, your majesties, but the monsters have returned!"

In an instant, Celestia was alert. Next to her bed stood a suit of golden armor. She donned a breastplate set with amethyst and shoulder guards that matched. A plated neck guard, jointed to allow flexible movement, and a helmet tipped with two pointed horns that were set with amethyst protected her head. On her legs, she wore fleured leg braces which wrapped their forms around her hooves and came to points at her knees. Her pale, sunrise-hued mane flowed majestically behind her as she sprang to the window.

"Hurry, Luna!" Luna's own armor formed around her body as Celestia swiftly flew toward the small village at the base of their castle. When Luna caught up to her sister, she was already challenging the beasts which threatened her people: Canis Majors, the starwolves.

A group split off away from Celestia while she was distracted and attacked a group of undefended ponies. The ponies screamed and ran, but the wolves were far too quick to be simply out run.

Luna teleported in front of the pack, her horn glowing bright as beams shot out and struck the wolves. They yelped and turned tail back toward the forest which lay at the edge of the village. She then turned her attentions back to the main group.

Luna watched as Celestia rose into the air, her horn shining like the sun. Suddenly, a streak of fire blazed forth and lit the pack. They howled and ran back toward the forest. But then Celestia appeared before them and blocked their path. She sent another blaze straight through the wolves, consuming them in flames. Her eyes burned white, and her mane flared like the flames before her until the wolves were nothing but dust. Satisfied that her work was done, Celestia flew back to the castle, where she would surely remove her armor and curl up like she had the past few days.

As Luna watched her fly away, the townsponies crept out from their homes to see the threat was gone. Cheers fell on her ears as she spread her wings and followed her sister back to the castle.

\When she landed, she noticed Celestia hadn't taken off her armor yet. Instead, she was sitting on the pedestal which overlooked the forest and distant Ponyville.

"Is there something the matter, Tia? Thou hast yet to remove thine armor. Dost thou fear for the townsponies still?"

"I don't know what's happening to me, Luna." Celestia said without turning her head. "I killed them. I killed them all. Not only that, but I didn't even care that all of Ponyville was watching."

"Dwell on it not. Thou didst as thou thought best," Luna consoled.

"You're right... I defended out subjects. I did what was best." Celestia turned her head to face Luna, who was now standing beside her. "But the threat still remains, because you didn't do that. You let some escape." Celestia's eyes firmed and became resolute. "Why?"

"Because the creatures of the forest are as much our subjects as the ponies."

"No, Luna. They are just a disease that poisons the land and must be exterminated to protect the ones that truly matter."

"Thou art not thyself. The Celestia we-- I, know would not so quickly destroy any creature within her domain. Rest thy body and mend thy heart, sister, lest-"

"Or what, sister?" Luna became silent as she watched her sister subtly transform. Even the sky around the castle began to swirl into an ominous cloud from the magic that was swirling through and around Celestia.

Luna suddenly recognized the evil that had grown inside Celestia's heart, but it was too late. She cursed herself for her ignorance. That same evil had claimed her just over 1000 years earlier, and she knew how difficult it was to fight.

"Luna, by your actions, thou hast proven that thou cannot be trusted to do what is best for our subjects." At that, Celestia's mane grew dark, flowing like the blue beginnings of a flame. Her face became hard, and her eyes became slit like a dragon's and glowed a deep purple. The sun began to rise behind Celestia, displacing the night and casting a ray of light behind her which glistened against her armor. "Luna, thou art no longer fit to rule by our side. We shall take thy half of the kingdom!"

Celestia's mane and tail exploded like a blazing Corona, and her eyes gleamed a pupil-less white. Her horn glowed, and her assault against Luna began.