Flight of the Valkyrie

Celestia suggested, "Maybe you should learn how to control your powers before you go off to fight. We don't want you to hit one of our own."

Mist asked, "What do you mean?"

Celestia smiled. "A costume change isn't going to change much. Focus your energy into your hands."

Mist concentrated, and to her evident surprise, a flamelike golden aura of magic formed around her hands. "Is this...magic?"

"In fact, yes. What you now possess is powerful light magic that can drive all but the most powerful dark monsters with ease. However, you must try to rein it in. It could have disastrous consequences on everything within miles if you were to lose control of it."

"Teach me, princess.”

Luna was afraid. So very afraid and confused. She could sense that something was pressing against this world, trying to find a weak spot in this world's very fabric. Even in the dreamscape she could feel the tremors of the dark, something she had not felt since the Tantabus had escaped from the confines of her mind, since Nightmare Moon was inside her. Nightmare was no longer a threat, but Luna felt certain something malevolent was out there. And she was powerless to stop it. She absently fiddled with her black crown. As Luna stood with her night sky colored ethereal hair flowing and her hands hanging by her dark blue dress, she stared out at the world on her balcony until she felt a large tremor of powerful magic coming from the secret cave. Luna gasped, and flew off to find her sister.

Luna burst into the throne room. Two figures looked back at her. One was her sister, Princess Celestia. But the other...the other was a flame-winged dragon hybrid with narrowed golden eyes. Luna summoned her sword, Moonlight Edge, and pointed it at the mysterious stranger. “Sister, who is this person? We felt a tremor from the cave,” Luna growled in the Royal Canterlot Voice.

“You can call me Mist,” the stranger said.

“Well...Mist, what business do thou have to be here? Thou certainly does not come from this world, nor have we ever seen anyone like thyself."

“Luna!” Celestia scolded.

“Well, sister, why art thou trusting this stranger so steadfastly? It seems to us that no one can be trusted that comes from another world entirely.”

Celestia sighed. “Sister, however much you may distrust Mist, there is a much bigger threat coming if we don’t find more allies. Something dark is out there, and I’m sure you can feel its presence pressing against our world as of late.”

Luna shuddered. "And thou art correct. It is all we can do to keep it out of the dream realm."

Celestia nodded. "This is why Mist has come. She was driven out of her world by a monster of these forces, and has come to seek help and help us. You do remember two thousand years ago?"

Luna scowled. "Yes, sister. We do remember. But first, let us test this new ally of yours, shall we? Mist, we challenge you to a sword duel! The terms are thus: whoever succeeds in grounding the other three times is the victor! Killing is forbidden, and if thou should win we will help thou defeat this enemy. If we win, however, thou must leave Equestria. Does thou accept?"

Mist got into a fighting position. "Let's battle!"

Luna: 0
Mist: 0

Luna cast a barrier spell over the area they would be using, then spread her wings. "Take to the air." Mist did so. "Go!" Luna flew at Mist. Quick as a striking snake, she slashed at Mist, only for the sword to get blocked by a fiery sword that Mist had drawn. Then Luna used a large overhead blow to knock Mist out of the air. Luna smiled. “One for me.”

Luna: 1
Mist: 0

Mist stabbed forward with her sword, only for it to get parried by Luna! Then Luna flew upwards and behind Mist in a blur too fast for eyes to follow. Mist felt a presence behind her, and dodged to the side just as Luna brought her blade down! The flat of the blade hit Mist, causing her to lose her balance and careen to the side. Mist fought to regain her balance, and struck at Luna’s side, causing Luna to fall to the ground! Luna struggled to her feet, and used her magic to heal the wound, which was bleeding. “Not bad. I’ll allow magic to fight now. Let’s see how you can handle that!”

Luna: 1
Mist: 1

Luna charged up her magic and fired a blast of pure white energy at Mist, who couldn't fly fast enough to get out of the way! It hit Mist squarely in the chest and sent her crashing to the ground.

Luna: 2
Mist: 1

Mist retaliated by flying up high, then firing off a succession of rapid-fire blasts of flames! Luna dodged every single one, then flew at Mist with her sword coming down on Mist's wing! The blade missed by a feather, and Mist lunged at Luna, clipping her wing and knocking her to the side of the barrier! Luna slid down to the floor, but just as quickly got back up and slashed at Mist!

Luna: 2
Mist: 2

Mist dodged and charged up a fireball in her right fist before lobbing it at Luna, who crashed down to the ground, batting at the flames. The flames finally out, Luna looked up and scowled.

Luna: 2, lose
Mist: 3, win

"So it seems I have to help. Very well, just don't get in my way. And if anything bad should happen involving you to our forces, the consequences will be grave. Other than that, I hope we will be able to tolerate each other." Luna walked out of the throne room.

Celestia sighed. "I'm so sorry about that...interruption. Perhaps it's time I took you to meet the Bearers of the Elements of Harmony. Let's see if they are more friendly than my sister."