Twilight Sparkle and her friends, Spike and Discord included, quickly ran into the cave. Standing before them was the Tree of Harmony, and below its large, crystalline form was the mysterious box that had appeared a few months before, after they had saved it from an invasion of malevolent vines. Sticking from it already were five, golden keys; each provided by their respective ponies, and the element they represented.
Twilight approached the only empty keyhole as everyone watched, and looked at her triangular-shaped necklace, given to her by the repentant Discord. With a deep breath, she lifted the necklace to it, and a purple cloud of magic grabbed ahold of it from her, and spun it around in the air above at a blinding speed. Once it was done, the item had visibly been transfigured into the shape of the final key.
Twilight and her friends smiled as they watched the object slowly drifted down to the remaining hole and hold fast. A feeling of joy went out through the room at their success but the feeling of tremors shaking below their hooves caused the look to vanish; the magnitude of the situation catching up with them all.
"Together!" Twilight spoke to her friends, giving them each a confident look. "I think we have to do this together!"
The six ponies walked forward and simultaneously placed their hooves on their respective keys. Just feeling the objects gave each of them a feeling of vigor and returned strength, considering how it had been taken from them by that centaur. As they were beginning to push in and turn the devices, a horrendously loud roar from Tirek, followed by a more powerful, earsplittingly-thunderous quake from the earth suddenly went out, nearly knocking over every pony there.
"What in tarnation?" Applejack exclaimed, as she fixed her now-crooked hat. "Just what in the hay was that?"
Spike and Discord walked to the edge of the cave, and seconds after looking outside, shocked expressions were painted onto their faces. "Um... guys..." the young dragon began, motioning for them to come to where he was and observe what he and the draconequus were witnessing. "You might wanna come see this real quickly..."
The six ponies trotted over with concerned thoughts and took a peak outside. What each of them saw, far in the distance, was the shape of Lord Tirek. However, he appeared to be attempting to attack something, and the frustrated, if not downright furious look on his face showed how he clearly wasn't having any fun doing it.
"Holy smokes!" Pinkie Pie cried out. "What's going on over there?"
"I have no idea," Twilight replied, as her eyes squinted and caught sight of a small shape that the mountain-sized centaur took another, sweeping swing at. "It looks like somepony... or some thing is fighting Tirek."
"And is it me, or does he look like he's not getting hurt at all?" Rainbow Dash brought up, having seen the same figure. A serious expression came over Twilight's face, and she looked back to her friends gravely.
"I think it's safer of we activate what we found, and make sure their fight doesn't destroy all of Equestria," the purple mare spoke. Her friends quickly nodded in agreement, and followed her back into the cave where the box was. Quickly getting back into their previous positions, they each turned their keys with a click.
Gasping in awe, they saw as the box opened up, revealing a white glow. A rainbow then emerged from it, and connected from the box to the Tree of Harmony, slowly allowing the elements on its branches to glimmer brightly...
The ground shook and split asunder as Tirek slammed both of his fists into it, scattering boulders and rocks. The surrounding landscape was decimated by a beam of orange magic he sent out. The centaur even tried to clap his hands together like a person attempting to squash a gnat, but with every swing of his fist, kick of his hoofed leg, or blast of magic, Boros only dodged each attack with complete ease. So far, he hadn't even attempted to attack Tirek; he was only observing his power, seeing if he was as strong as predicted.
"I have traveled far and visited many places in my quest for a proper fight. When I came here, I thought for sure this was where one native life form like yourself could at least hit me!" the alien shouted to his foe in a mocking voice, as he jumped up and floated directly in front of him, letting his dark, crimson cape flutter in the zephyr created by Tirek's last gigantic swing. "Quit this doltish droll and give my existence some more... stimulation, Tirek!"
"I'll show you stimulation you cocky, one-eyed freak," Tirek bellowed, suddenly sending his enormous fist forward at a much faster, nearly unobservable speed then it was going before. Honestly not expecting this kind of sharpness from him, it hit Boros directly before he could so much as react and threw him to the ground with a massive, concussive force, creating a shock wave of sound that flattened nearby trees and another, deep crater as he slammed into the forest below. Deciding against giving him time to recover, Tirek began to charge a powerful spell, letting the space in between his horns glow as a bright, orange sphere of magic formed. When it was done moments later, he sent it out as a powerful pillar of pure energy that blasted through the crater, and cut through the ground and forest in front of it.
Tirek smirked and couldn't help but chuckled quietly to himself as he saw the unparalleled devastation he had caused. When the dust finally settled however, his snickering stopped when he saw what had actually become of his adversary.
Lord Boros still stood in the pathway of the beam, hunched over, smoking rising from his form, and fully alive and well by the looks of it. His armor had been badly damaged by the attacks Tirek imposed, and most of it had been destroyed or removed from his upper body, revealing how skinny he looked underneath. As he stood up straight, the majority of what armor pieces remained fell off limply, and what still clung on loosely was physically shed by his own hands.
"This set of armor, used to seal in my immeasurable, irresistible power..." he spoke in a voice as low, quiet, and intimate as a whisper, as the last charred flakes of the metal that had been covering him fell to the ground with a clatter. "...Has been broken."
"What?" was all Tirek was able to ask with a confused look, unaware of what storm was about to come his way.