Them

She was feeling dizzy. Never before she had to stay up all day, much less raise the sun. She hadn't had a good day or night of sleep in a long time. If somepony or something decided to attack her, she wouldn't stand a chance. Fortunetely Captain Shining Armor was always by her side.

"Are you sure you don't want me to raise the sun for you, aunt Lulu?" asked Princess Cadence, sounding extremely worried.

"Yes, I am entirely sure, Cadenza." Luna said. "This task requires a very experienced Alicorn to perform the spell and, as I recall Tia telling me, you've been one by barely ten years."

"But--"

"Maybe you'll be able to take my place in fifty years or so."

"But I gave up on my immortality so I could marry Shining Armor." she looked at her husband, who gave her a warm smile. "And I have no regrets!"

Luna affectionately nuzzled her niece, who nuzzled her beloved aunt back.

"I'm sorry, Cadenza, but you can't." she sat back on her late sister's throne. "Anyway, if Tia could do it, so can I!"

Cadence sighed. "If that's what you wish..." she walked toward the exit of the throne room. "If you need me, I'll be in my bedchamber. Good night, aunt Lulu. Good night, Shining Armor." using her magic, she closed the doors behind her.

"She may overestimate her abilites, but her heart is in the right place."

"She was always like that." Shining said. "Since kindergarten."

"I can see why you married her!"

Shining Armor's horn sparkled for a second and he sighed. "Time to re-cast the spell." he walked to the balcony and looked down at the city. He thought about the stallions, mares and foals that were counting on his shield. So many lives would be lost if he failed again. "Last time there were no casualties." he thought. "But one stallion can't be that lucky twice. This time they are not Changelings. I will not fail! Ever again!" he closed his eyes and fired a beam of magic at the pink protection bubble surrounding the city, making it ticker and stronger. Shining Armor then went back to Luna's side.

"You shouldn't take all the responsibility, Captain. Remember, you are not alone."

"But I'm the only one who can cast a shield spell that large."

"I'm not talking about that, Captain Shining Armor, and you know it. I'm talking about what I see in your eyes. The sense of duty, the compassion and, above it all, the blame. Everything that happens, you blame yourself, even though you had nothing to do with it."

"I am the Captain of the Royal Guard, it's my responsability to protect everypony! And even that I can do right..."

"You are so much like your wife. Both of you have your hearts in the right place. The only difference is that you underestimate your abilites and blame yourself for everything! You can't protect everypony, Captain. Nopony can. Not even I, neither my late sister could. But that doesn't make you a bad Captain."

"But--" Princess Luna nuzzled Shining Armor's neck, making him blush. "Y-Your Highness?"

"I am old, Captain. I met many Royal Guard Captains, but none like you. They were all 'duty slaves', doing nothing but what they were instructed or had to do. You are different! You have a heart, you show your feelings, you're always willing to do what's right and always trying to be a better pony than you were in the previous day. I dare to say you are the best Royal Guard Captain I came across." she smiled. "Now stop blaming yourself and turn back into that grat Captain I met after my return!"

Shining Armor smiled and saluted her. "Yes, Your Highness!"

A loud boom echoed through the city and Shining Armor groaned in pain.

"Something wrong, Captain?"

"My head. It hurts."

Another boom. Shing Armor groaned again, but this time he feel to the floor. The doors were opened again and Cadence walked in.

"Did you heard-- SHINING ARMOR!" she quickly ran toward her husband and helped him up. "What happened, dear?"

"My head!"

"Don't worry, I'll take you to the infirmary immediately and they'll--"

"No, those aren't spell-casting headaches." he said. "The shield is under attack. And the attacker must be monstrously strong, since I can even feel the--"

Another boom, another pained groan.

"You need to lie down, dear. Let's go."

Cadence left the room carrying her husband. Luna walked toward the balcony; what she saw made her gasp:

"T-Tia..."

The infected Celestia was outside the shield, attacking it with red magical beams.

"I-I don't understand. Why is she here? She wasn't supposed to be here!"

"Princess Luna!" called a voice from the corridors. She turned around and saw her sister's former student, Twilight Sparkle and her assistant, Spike the Dragon (who was quite taller than the last time she saw him). "It's Princess Celestia! She's... She's..."

"I am aware of that." Luna's horn started glowing and a dark blue armor materialized around her body. "Completely aware."

"A-Are you going to...?"

"Yes. Looks like banishing her to the sun didn't worked, only made her angry and toasted. I have to finish this myself!"

"But what... What if you... Fail?" Spike asked.

Luna smiled. "If I fail, then I want you to gather the strongest unicorns in Equestria and keep raising the sun and the moon together. Maybe monarchy is getting quite old, don't you think?" she flapped her wings a few times before taking off. "This probably is going to be the longest night of Equestrian history."

* * *

Luna woke up a little later than usual that day. It wasn't sunset yet, but she knew it was past the timeCelestia usually lowered the sun.

"That's weird." she thought. "Why is Tia extending the day?"

She adjusted her crown and shoes before walking to the throne room. Her eyes widened when she saw blood everywhere and dead ponies lying on the ground all over the room. Celestia was standing there, looking at her.

"Oh. Luna. I'm terribly sorry, I forgot to wake you up."

"What is the meaning of this, sister?!" she asked, almost shouting.

"They are sick, Lulu. A sickness that has no cure. It consumes the brain and turns you into a killing machine. And the worst part is..." she presented her right forehoof to her sister, which had a dark bite mark on it. "It's contagious."

"T-T-Tia... Tell... Tell me this is a joke. A cruel, sick joke of terrible taste!"

"I wish it was, Lulu. I really do." she sighed. "I suppose you are good with long-ranged teleportation spells, right?"

"Y-Yes, quite good, but why do you ask?"

"We both know that we are far too powerful to be killed by mortal ponies, even at our worse, and I don't want you to force you to end my life."

"Wh-What are you trying to say, Celestia?"

"I can turn into one of them at any moment, Luna. Once I lose control of myself, please banish me to the sun."

"Wh-What?! But... But..."

"I doubt my mindless self will be able to protect herself from the heat of the sun or figure out a way to return. I'll just burn forever, never being a threat to any of my subjects. Or you!" she nuzzled her sister's neck. "So, while I still myself, I want to spend my last moments with you, my loved sister."

"T-Tia... It... It doesn't need to be like this..."

Celestia kissed her little sister's forehead.

"Yes, it does."

"Celestia!" she hugged her big sister, staining her pure white chest with her tears. "I don't want you to go! I don't want to lose you!"

"I didn't want to go either, but you lost me the moment I got bitten. It just doesn't look like I am. Yet. This is my final moment, but at least I can die happy, since you finally were able to understand the magic of friendship. But here's an inevitable part of this magics: eventually friends have to say goodbye."

"N-No..."

"Goodbye, Lulu. I love you, dear sister."

"I love you too, Celestia. You hear me? I love you, love you, love you!"

"Never forget Luna; I'll always be in your heart!"

"I will never forget you, loved sister."

Celestia smiled before groaning and falling.

"S-Sister!!"

"M-My time has come." Celestia said. "Do it."

"But--"

"NOW!" her shout made the whole room tremble.

Luna was scared. She hadn't hear Celestia's Traditional Royal Canterlot Voice in a thousand years. Her sister was obviously losing control. She closed her eyes, he tears still flowing. She didn't wanted to watch herself banish her sister.

Celestia's scream of pain turned into a roar of rage. Luna's horn started to glow. After a big explosion of light, there was silence in the throne room. She opened her eyes and found herself alone in the room; Celestia and all the bodies had disappeared. She fell to the floor and cried more.

* * *

Shining Armor opened his eyes. The headaches had stopped. His wife hugged him.

"Oh, thank Luna, you're alright."

He looked around and noticed he was on an infirmary's bed. Not many beds were occupied, since it was only supposed to be used by royalty, guards and Science Team members.

"Where's... Where's Princess Luna?"

Cadence sighed. "Out there. Fighting."

Shining's eyes widened. He jumped off the bed and looked through the window; he saw the moon and two silhouettes fighting in front of it. One he recognized as Princess Luna, since she was wielding The Crescent Moon, Luna's favorite weapon. The other was familiar, but he couldn't point who it was.

"Is she insane?!" he shouted. "Wait a minute, is that the Changeling Queen again?"

"It doesn't look like her."

"Because Equestria is already bad enough with one threat. Two would be just awful!"

"All we can do is sit back and hope she defeats C-- Whatever that thing is..."