As Fluttershy followed Matrixwing, she tripped on a rock. She failed to catch herself, and was sent tumbling down the slope. She knocked Matrixwing down in the process, rolling them both deeper into the cave. The torch went flying as the pair slammed into something very large and wooden.
"Oh my, I'm so, so sorry..." Fluttershy turned scarlet in embarrassment. "It's alright, Fluttershy. Are you hurt?" Matrixwing stood and pulled Fluttershy to her hooves. "I'm okay," Fluttershy replied.
After helping Fluttershy up, he looked around in the darkness for the torch. He saw a faint glowing outline of the torch sitting next to the outline of a brazier, and picked it up. Then he relit the torch (as well as the brazier for good measure) and walked over to where Fluttershy was waiting. "That's better," he said.
Before Fluttershy could say anything, flashes of light erupted from behind Matrixwing. She yelped, which caused Matrixwing's eyebrow to raise questioningly. "What is it?" He levitated himself with his wings and spun around. A somewhat elliptical door was there, with glowing runes from the bottom of one side going all the way up and around to the bottom of the other side.
He recognized the runes as Ancient Equestrian, and began to translate them unconsciously aloud: "Here lies Corefire, the Element of Hope. Sun Aura Caverns are her final resting place, because they are also her home. Any adventurer who do not hold the Elements, or the Hope will never see the inside of this door."
Suddenly, the door began to vibrate and hum, then it swing open silently with a blinding flash of light, revealing an enormous cavern with sunlight streaming out of several holes in its ceiling.
As Matrixwing and Fluttershy stepped through the door into the cavern, they gaped at the vastness and beauty of it, marveling at the beauty. Small waterfalls ran through a few of the holes, making the light reflect rainbows across the walls of the caverns. It seemed that the caverns' name was perfectly justified.
The cavern itself was about twenty stories high and about half as wide as the Crystal Empire. Tears began to well up in Fluttershy's eyes. "It's so beautiful," she commented. Matrixwing said something intelligent like: "Ungh-huh... Whoa..."
They stood in silence for a few minutes, leaning into each other, then Matrixwing spotted something below them. "What's that down there?" He pointed out a small cobblestone platform with a pedestal and a wooden casket upon it. "Let's check it out." Matrixwing held onto Fluttershy's hoof with his own and they both flew down to it.
When they finally got down to the casket, it began to glow on a certain spot. Matrixwing examined the glow and found it to be more runes. He read them to himself: Hope. The casket itself was a hexagonal shape, and had a large clamp on the front of it.
Matrixwing picked up the casket into his hooves. He sat on his haunches and tried the clamp. It wouldn't open, even though it had no keyhole or lock. Matrixwing began to try multiple methods, including flying up and throwing it into the ground with all the strength he could muster, but nothing would open the casket.
"There has to be a way to open it," he said these words to himself, "and I'm not stopping until I do! We need this element, I know that there is a way to get to it." Almost immediately after he said these words, the casket un-clamped and popped open, revealing multiple dull gem fragments sitting in the arrangement of a circle, with the largest in the center.
Matrixwing was about to ask what the gems were when they flew out of the casket, encircling Matrixwing like a small dance party. Then, the gem fragments began to abruptly zip towards Matrixwing's chest, generating a bright golden glow from it. He rose a few inches off the ground, the lightning in his eyes turning into a pure white color.
As this happened, Fluttershy remained silent, watching as Matrixwing slowly grew brighter. Then, the light slowly dimmed as he floated back down to the cobblestone platform, around his neck was an amulet, encrusted in it was the Element of Hope. It's shape was that of Matrixwing's cutie mark, except the cloud and bolts of electricity were the color of bright gold.
"What... just happened?" Matrixwing was now aware of the amulet around his neck. Fluttershy trotted over to him. Then, as she nuzzled Matrixwing's chest, she told him: "You were chosen as the seventh Element..." Matrixwing blushed furiously, then he asked quietly as he wrapped his forelegs around her: "Ready to save everypony?"
"I-is it going to be dangerous?" Fluttershy asked this fearfully, but she already knew the answer. "I believe it will be... but I hope not. If it is, I'll protect you. I'd gladly give up my life for yours," Matrixwing replied. Fluttershy responded quickly: "It's not going to come to that!"
She hugged Matrixwing tightly, a lone tear dripped from her eye onto his chest. "Hey..." Matrixwing stroked the back of her head. "It's alright, you won't lose me."
They stood like that for what felt like an eternity, then Fluttershy calmed down enough to tell Matrixwing: "We need to get back to Canterlot, the girls are waiting for us." Matrixwing nodded, and adjusted his grip on Fluttershy. Fluttershy knew that they were about to fly, and braced herself by wrapping her hind legs around him as well.
Matrixwing then shot towards the ceiling, and through one of the many holes there. The torch that was clamped to his pack blew out and slipped out, falling to the earth below.
Fluttershy had been surprised by their speed that she began to hold on tighter, whimpering slightly as she did so. But Matrixwing kept concentrating on holding on to her and flight. They got to Canterlot in little over an hour, and Fluttershy started to feel a bit tired from holding on so tightly.
Suddenly, Matrixwing froze in midair. He stared at Canterlot silently, his eyes wide. "What's wrong?" Fluttershy asked as she turned her head towards Canterlot. She instantly saw what was bothering Matrixwing so badly.
Darkness covered the city, its tendrils creeping in and around everything: stores, homes, gates, nothing could escape it. The darkness was slowly making its way towards Canterlot Castle. Little creatures of shadow chased the residents, capturing them and changing them. Some appeared to be... eating the corpses of the dead ponies.
At the heart of all the darkness, trotting through the streets as if it owned Canterlot, corrupting everything it touched, was the Shadow itself, its dark body forcing fear deep into the hearts of everything that looked upon it.