The Immortals: Dark, evil creatures who can't raise their numbers, but can live on for an eternity using their power source, dark matter. Only the life-giving energy of the Sun itself has any chance of destroying these undead monsters.
There are many clans of Immortals who work to cast the world into eternal darkness and rule the new world. The clan that infiltrated into Equestria are known infamously as the Dusk clan, a trio of Immortal sisters lead by the eldest sister, Lady Gungnir.
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As they traveled to the landing site of the Dusk clan, Master Otenko gave Twilight Sparkle a rough idea on who he was. He claimed that he was the terrestrial embodiment of the Sun's will and wished to destroy the evil in his world. He went on about how he and the Immortals are from another world, possibly even another dimension, and made their way into Equestria to resume a battle. After a short and vague explanation, Twilight was left surprisingly unfazed.
"You seem rather calm after what I told you." Otenko said. "I'm not too sure how you ponies work here, but in my world, people probably would've panicked if they saw something they've never seen before, such as a talking, magical pony like yourself."
"Well Otenko, I've actually seen a lot of crazier things in my life then a talking, floating flower falling out of the sky."
"FLOWER!?" Otenko shouted with anger. "I am the terrestrial embodiment of the Sun's will! The Messenger of the Sun. I am...NOT...A SIMPLE FLOWER!"
"Alright, alright. Sheesh. Don't burn out on me." Twilight responded.
Otenko looked as if he was about to have an aneurysm, but it could be debated if he even had blood at all, but after blowing off a little steam, he managed to calm down. He also knew that there were more important things to talk about then his titles.
"I certainly hope you've been through as much as you said you have, because without my real partner, Django The Solar Boy, we're already at a severe disadvantage. How strong is your magic?"
"Well, I don't want to toot my own unicorn horn or anything, but-" Twilight said with a smile.
"Good enough. I'm pretty desperate, so you'll have to do. Now then, I'm sensing that the Immortals are just ahead of us. Let's move forward."
Satisfied by Twilight's answer, as he was willing to take whatever help he could get, Otenko pressed forward with Twilight following, not being happy with the idea of Otenko calling her a desperate choice, not being able to talk about her skills in magic, and of course, her new partner overall. She also wanted to tell him a bit about Ponyville and Equestria, but had to put that on hold until she could find the proper time.
What probably bothered her the most though was that she still knew hardly anything about what was going on or who exactly Otenko was, but because there was clearly immediate danger, she knew she had to wait a while longer before sharing and learning anything else.
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At the other landing site, the purple and yellow orbs of light rose up in the air as they saw the blue one enter Rainbow Dash's body. However, it was no longer Rainbow Dash that was even there. It was one of the three Immortals.
"Hasty as always, huh Mjolnar?" The purple light said, which was followed by a deranged laugh.
"Nah, I only pick the bodies that appeal to me, and I just happened to of liked this one." Mjolnar said, still gazing at her new body with pride. "The ponies of this land must be beautiful. I feel really strong in this body too. Great for destroying things."
"Now now. Don't do anything reckless yet." The yellow light said. "We still have a lot to prepare for. Me and you're younger sister still need bodies of our own, and I don't think they will be walking right up to us like yours did."
"Hehe. That means I can destroy the village over there ALL by myself."
"Calm yourself. I will let you destroy it, but in an organized manner. There's a difference between causing chaos and being stupid."
Mjolnar made Rainbow Dash look calm and collected in comparison. She loved nothing more than to break and destroy things, preferring to mindlessly obliterate everything in site than to think about her actions. She was truly a trigger happy Immortal. Unfortunately for her, Gungnir, the yellow light, preferred organized chaos.
"Now then, since we've entered this new world, Otenko likely did as well. He did follow us here after all.You are to lure him away from here so me and your sister can get bodies of our own without any threats. Once all three of us finally have physical forms, we can dye this land red."
"So I can destroy Messenger of the Sun himself?" Mjolnar asked with a smile on Rainbow Dash's face. "That'll be better than destroying the village ten times over!"
"That's not going to happen, Mjolnar!"
Much to the Immortal's surprise, Twilight Sparkle and Otenko both overheard the sisters talking, since the two had arrived at the landing site. Otenko spoke out with fury as he challenged the Immortals, but what Twilight Sparkle saw left her confused, as she found it odd how Rainbow Dash was behaving.
"Rainbow Dash! What are you doing? I thought I told you not to come here." Twilight said.
"That's not a friend of yours, Miss Sparkle. At least not anymore." Otenko explained. "It appears that Mjolnar has taken over her body."
"What? WHO!?"
"The Dusk sisters don't have true forms. They live and fight by binding themselves into a mortal body and using that instead. Your friend has been completely taken over!"
"And what luck, too." Mjolnar said. "According to the memories of this pegasus, I'm apparently one of her best friends. Hey Twilight, remember those times when I did my Sonic Rainboom?"
Twilight was not at all pleased with what Rainbow Dash, or rather the one who possessed her, said. On top of that, Mjolnar tried to act as Twilight's old friend. Angered by how one of her best friends had somehow transformed into something evil, she charged in to attack Mjolnar horn-first. Twilight wouldn't normally be so brash, but after seeing her friend captured, she wasn't able to think rationally.
The problem was that she didn't understood who she was facing. In response to Twilight's charge attack, Mjolnar opened up her wing, and with a single flap, created a mighty gust of wind which blew the off-guarded Twilight back several feet. Wind magic was a specialty of Mjolnar, and the body of the pegasus reinforced that strength.
"Oooh, I see we have a challenger!" Mjolnar said with glee. "If you really want to start a fight with me, you have to catch me first!"
Excited to have such a chance at destroying one of the sisters' most hated enemies, Mjolnar opened up her newly acquired wings a second time and took off to the sky with great speed. Twilight, refusing to let Mjolnar take her friend away, took flight as well and began pursuit.
"Miss Sparkle, wait!" Otenko said as he chased after Twilight.
And with that, the remaining Dusk sisters were alone. Alone to do whatever they wished without interruption.
"Yes. YES! Time to cause absolute chaos and horror!" The purple light said with glee.
"Calm yourself. We are to claim our new bodies and hide." Gungnir said. "The more we stick out, the less time we get to regain our full powers. Until we're at full strength, we can't defend ourselves against the ones we are after, nor can we succeed in our ultimate goal."
"But, but, but...the pain and suffering!"
"Will come later. Our bodies come now. If we have enough time though, I'll let you kill some people or ponies or whatever on our way out."
"YAY! MURDER! I sure hope these ponies taste good." The purple light said.
As they got their priorities straight, the lights of the Dusk sisters crawled their way out of the crater and made their way to Ponyville to get their new bodies while their middle sister dealt with Twilight Sparkle and Master Otenko alone.
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"Twilight, please slow down a bit!" Otenko said as he rode on Twilight's back. "We still have much to talk about."
"Unless you want to talk about how to kick that friend snatchers' butt, I'm not interested." Twilight said.
"As a matter of fact, that's exactly what I want to talk to you about."
As she was pleasantly surprised by Otenko's answer, Twilight stopped her high-speed chase to talk to him. She also realized where she brought herself, which was by a large mountain. Twilight was once at the mountain with all of her friends when a dragon took residence there and caused trouble as it slept, but that's a completely different story.
"First things first. I need to set up the Pile Driver." "Otenko explained. "Take us to a large clearing close to the mountain."
"Pile Driver? What the hay is that?" Twilight asked.
"The Immortals are powerful beings who can not defeated by ordinary means. For us to have any chance to purify and destroy Mjolnar, I'll need to set up-"
"Whoa whoa! Wait a minute!" Twilight interrupted. "You want me to destroy Rainbow Dash?"
"Hmm...yes and no." Otenko answered. "It's true, we will have to place your friend into the Pile Driver, but it's only expected to kill off the Immortal."
"EXPECTED? Are you telling me there's a chance your pile-thing will kill Rainbow Dash? Forget it." Twilight said as she landed on the ground. Then, she used her magic to take Otenko off her back and dropped him on the ground. "You stay away from Rainbow Dash. I'm going to rescue her alone."
As she hated the sound of the technique Otenko wished to use on Mjolnar and Rainbow Dash, Twilight abandoned Otenko and continued her chase after her friend alone. She was too worried for her friends' well being to risk killing her.
"MISS SPARKLE! COME BACK!" Otenko shouted, only for his cry to fall on deaf ears. "Just my luck. There's probably a million ponies like her in this world, yet I got stuck with the stubborn princess. I think I've taken Django's quietness for granted. He never argued with me."
As annoyed as Otenko was, he knew how important the Pile Driver and was perfectly aware by how it was the only way to save Rainbow Dash. He also knew that Twilight Sparkle would realize that she would have no choice but to use the Pile Driver to save her friend.
After giving a quick check of the area he was in, he found that it was flat and wide enough for him to summon the Pile Driver. Despite Twilight's complaints about using something that's meant to kill, he intended on having it be summoned, then later used.
"I'd best do it now before I lose Miss Sparkle." Otenko said to himself. Then, after glowing a bright light from his body, he lets out a mighty shout. "TAIYOOOOOOH!"
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At that time, the other Dusk sisters searched around Ponyville with great stealth to find themselves new bodies. They could've done what Mjolnar did and grab the first body they could find, but Gungnir was much pickier than that.
"Filthy animals. That's what they are." Gungnir said to herself. "The humans back in my world at least had the dignity to cloth themselves, despite being lower life forms! I don't care what Mjolnar said earlier, these ponies are more hideous then...wait a moment... "
As Gungnir searched the town for a host, she found a pony that managed to stick out of the crowd. A beautiful, white coated mare with a unique purple mane-style. She was with a filly that looked similar to her and a purple, baby dragon. The younger ones were carrying different types of fabric for the mare.
"I'm very thankful for the help, you two, and considering that Twilight wants every pony to stay inside. It'll at least keep you two busy."
"I'd help you even if it was the end of the world." Spike the baby dragon said with hearts in his eyes.
"And I still think making clothes is my special talent." Sweetie Belle, Rarity's sister said. "Between the two of us, we'll make the best outfit ever!"
After Sweetie Belle and Spike gave each other a high-five, or a high-hoof, depending on how you look at it since Spike has fingers, the two ran back to Rarity's clothing shop, her boutique, to get started on making their dress. Besides being happy with getting free labor, Rarity was happy knowing that the kids were being calm about everything that was happening in Ponyville at the time.
"Well, at least the skies are starting to clear up a bit. Maybe Twilight already fixed everything." Rarity said to herself. "On the other hoof, I am a little behind on my orders and could use the help."
As Rarity thought that there was nothing wrong happening, she smiled on her way home. Sadly, she was completely ignorant of the true danger ahead, or to be more precise, behind her.
The yellow light of Gungnir took an immediate liking to Rarity's appearance, having the beauty and grace she desired. After finally making her choice, Gungnir quickly moved to Rarity to claim Rarity's body for her own. At that point, Rarity finally sensed danger, but with the little time she was giving, all she could do was turn around to let out a bloodcurdling scream.
"AAAAHHHHHH!"