Sunset Shimmer had planned it all out, to the tiniest detail, so she could claim the Element of Magic and ascend to being a being of incredible power, an alicorn like her old mentor, Princess Celestia, where she had considered it her birthright as soon as she discovered it. Of course to do that she had to leave for another world, partly because of an argument over her princesshood and the fact that Celestia bestowed her power to some random pegasus, who became the 'Princess of Love', a fact that made her sick when she thought about it. The other part was due to the fact that time worked differently between her home world and the world that was on the other side of the mirror portal, because, as she had soon discovered, time moved far slower in the odd school world she had found herself in. Such a thing meant that, with her calculations, she could she could skip multiple years in her home world and await the awakening of the Element of Magic, so when she made her return it would be a simple matter to snatch it, return to her new world, and become a being of pure power.
She discovered a few interesting things about this world, everypony from her home world had a counterpart in this world, humans to be exact, and it also cut her off from her magic since none existed in the new world, which had been factored into her plan once she discovered it. Part of her plan also involved breaking the 'Friendship of Magic', so she had to enroll in the local school, where Sunset found she was fortunate that her counterpart was elsewhere in the world, not to mention a lot of sleepless nights figuring out how to hack and everything, before she could set up her plans. Once she was a student she proceeded to dominate the school with her iron fist, causing students and teachers to fear her and her wrath, to the point where she drove five childhood friends apart with her lies and rumors, much to her glee. Sunset also extended that to a local apartment area, as she had figured out a way to get free rent without the owners calling the cops, and even if they did there was a fair chance they wouldn't know who to look for.
Of course the only thing she hadn't originally intended on was for the portal to close on her, trapping her in the world on the other side of the mirror, so she had to put up with three years of school and the same routine to force everyone to maintain their dislike of each other.
The other pitfall in her plan was that the crown that was the Element of Magic had been taken by Principle Celestia, the counterpart of her old mentor, and she informed them that it was the crown that would be given to the one who won the Fall Formal, which Sunset would win in no time. At least that had been her thought at the time, only for Princess Twilight Sparkle, the one chosen by the Element of Magic, followed her to the mirror world and forced her way into the hearts of the students, finding ways to bridge their old connections and reforge relationships. It was a complete disaster, all of her plans upturned by one upstart princess who didn't deserve her power or position, and Sunset found that everyone, save for the local idiots, turned on her to support the one who helped them regain their connections. It had forced her to take drastic measures by threatening to either shatter the portal back home, to trap them both in the mirror world, before she threatened the little dog that followed Twilight, which, after some doing and effort, gave her her prize.
She had to admit that the sheer power that surged into her, even if it meant darkening an Element of Harmony, burned a little as it transformed her into what could only be described as a devil form and gave her the power to brainwash, even transform, the students into her personal army.
Her plan, despite it's various hiccups, had been successful and she had the power to overturn her entire world, where she would use the army to take down the various cities and towns, to make more followers, while she focused on beating the Prinnesses and breaking them with her mental powers. She had even demonstrated her power by twisting the idiots that followed her into their own devil forms, crushed part of the school to access more of the students, and seized control of the minds of the students, much to her joy. Of course Twilight thought that she could win and overturn her changes to the world, that she could stop her and right the wrongs that she committed, and, much to Sunset's annoyance, something in the immediate area gave both her and her new friends the power to stand up to her. Twilight claimed it was the power of friendship, that the bonds she shared with the girls, who happened to be the counterparts of her own friends interestingly enough, were enough to summon the power of the Elements of Harmony to this world and protected them from the blast Sunset had sent their way.
Somehow Twilight was able to connect with the crown and called upon the power of all six Elements, those being Magic, Honesty, Loyalty, Kindness, Generosity, and Laughter, transforming the six of them into what could only be called pony girls, as they were humans were pony ears sticking out of their heads, with extended hair and wings, if they were pegasi on the other side of the mirror.
Sunset had assumed that everything would turn out okay for her, that her dark Element would win against the true power of the Elements of Harmony, while Twilight claimed that, because she didn't possess the magic of friendship, she couldn't wield the true power of the crown. Such a thing allowed the unthinkable to happen, Twilight and her friends seemed to overpower the Element of Magic before forming a heart formation in the air, allowing them to combine the six Elements into a single beam of power that wrapped around her in a tornado of rainbow energy. They then undid her work, undoing the mind control on the students and liberating them from the magic Sunset had placed on them, especially when they got to her followers, before the Elements struck her repeatedly inside the tornado. As Twilight used more of the power on her, however, Sunset found that it was planning on smashing her into the ground before searing away the power that she had worked so hard to obtain, though she fought back to the best of her ability and refused to submit, or even accept, the scene that was happening before her eyes.
Despite Twilight's claims that she didn't understand the power of Harmony, and maybe she didn't, Sunset did know that the princess had overloaded the harmonic power, as when the tornado smashed her into the ground, causing pain to resonate all over her body, she ended up slipping through a portal that suddenly opened behind her, though she ended up blacking out in the process and slipped into the darkness.
The Lich King had risen from his long slumber, awakening the mighty Scourge from it's slumber and caused the forces of Death to stir once more, their undead bodies moving with ease despite the harsh winter conditions of Icecrown, which would slow and cripple any mortal warrior. It was here that his citadel, Icecrown Citadel, rested as it reached into the sky, forged from a metal said to be the blood of an Old God, making it incredibly sturdy and almost unbreakable, though he was currently out in part of the frozen wastes, enforcing his will upon the world. After awakening from his own slumber he had walked out of the citadel and made his way to where a mighty dragon had fallen a long time ago, supposedly during the War of the Ancients ten thousand years ago. Upon his arrival he had first made sure that he was in the right spot, as he found her body trapped below the ice, and drew his runeblade, a large two handed sword known as Frostmourne that was feared by mortals, where the Lich King channeled the power of Death into it before stabbing the ground.
His actions caused the power to surge into the massive skeleton that was buried in this area, which forced the ice to break as it, now reanimated by his power, emerged from it's long slumber, awakening the first of the Frostbrood, as he would call them, and allowing Sindragosa to roar as she soared over the Scourge, causing them to cheer in kind.
This was his power, the immense power of Death that the Legion sought to use against the people of Azeroth, to raise the dead into a force of darkness that would cripple the heroes of the Alliance and the Horde, two factions that battled each other and clashed every so often. While the factions were often at odds with each other both he and the Legion knew that, if they combined their forces, they could tear down most enemies that stood in their way, as they stopped one of the two leaders of the Legion from entering this world, much to his annoyance. Even before the factions existed most of Azeroth stood against the might of the Legion, finding ways to stop them from entering this world and banishing the leaders back to the Twisting Nether, often at great sacrifice for the races that called the world home. Such a thing was why he ordered his Cult of the Damned to find the coffins of great heroes, those slain either in conflict with the Legion, people they found to be allied with the demons, or even those slain while fighting the Old Gods, and opened the way for him to travel over to where they were resting, allowing him to make death knights of those heroes.
The Lich King's endgame was to unite the world in undeath, leaving nothing of life behind, so when the time came he and his forces could destroy the Legion, but to do that he first had to end the Alliance, the Horde, and anyone else that dared to stand in his way, namely the Scarlet Crusade.
As he stood near the edge of the cliff, overlooking his army of undead, the Lich King felt a change in the air as something headed towards where he was currently standing, causing him to turn his head towards the sky as it burst open and he found a meteor that slammed into the side of Sindragosa's former resting place. What he discovered was that it wasn't a meteor, a burning rock that would make a mess of the area that was around him, rather it seemed like someone might have teleported themselves to this place, as he knew there were mages capable of great things, in fact he had known one at one point in time. Sure enough the Lich King found that someone rested in the small crater that had been left behind, a young adult girl, possibly around twenty years old, who looked like she might have been in a fight before coming here, due to her strange clothing looking like it might have been burned in some manner. At first he assumed she was a human and expected to see such a body, before finding that her legs ended in hooves, similar to the draenei who now called Azeroth home, and she had a few other interesting parts, such as her pony tail, the pony ears poking out of her hair, and the horn in the middle of her forehead.
While he had no idea who she was, or what she was for that matter, he could feel the power coming from her, magical energy unlike anything he had felt recently, to which he stepped down to where she was resting and found that the sound of his metallic armor was causing her to stir. He suspected that she would make a great death knight if he raised her, in fact she might very well be the champion he had been seeking, the tool that would help him bring death to this world and allow him to fulfill his plans, but first she had to die. With that in mind the Lich King channeled the power of Death into his runeblade once more, causing an icy sheen to wash over Frostmourne's blade again, before he came to a stop in front of the stranger, whose eyes finally opened and allowed her to take in everything that was around her. In the next moment, before she understood what was going on, the Lich King drove his blade right into her heart, causing her to look down in disbelief for a few seconds, which was when the power of Death surged through her body like a plague, causing her body to go limp as the life left her.
In the next moment he pulled the blade free and channeled another power that it possessed, linking her soul back to her body, dragging it out of the afterlife essentially, where he found that her skin tone darkened, a sign it was working, before her eyes snapped open and showed him the icy nature of a death knight, but as she collapsed, however, he smiled as he called for the cultists to take her, as it was time to put his champion to work and he was looking forward to the carnage she would cause in his name.