I told you to go right

The herd charged, screaming battle cries and charging magic. I returned the favour; shouting 'Fuck You!' to those I hated, darting to the side to avoid magic blasts, the like. Finally, when I could nearly see the rage bouncing around Twilight's eyes as she led the charge, I leapt into the air with a sharp, wing propelled flap. Throwing myself over Twilight, Applejack, and a few other ponies I didn't recognise/absolutely hated, I opened both my wings with a sharp motion and jetted over the crowd.
"Shoot him down!" I heard Twilight order some others. Sure enough, sizzling magic bursts began to flick past my high speed body. All the spectrum colours could be seen; blue, red, green, yellow, lavender (no prizes), and eventually, black. I didn't even think the last one was possible. Just as I saw my exit, a small hatch behind the crowd, and began to head towards it, a massive jolt of burning enveloped my right wing. I yelled out in pain, dropped altitude slightly, and winced in pain as it felt like I was being corroded. I resisted the urge to look, and concentrated on reaching that manhole. A small window of opportunity arose when Thunderlane darted forward, ripped the hatch open, and usbered me inside. Shakily, I landed, stumbled, and fell into the manhole. It was dark in the sewers, and the light source was shut off when the lid was closed and bolted shut by Thunderlane.
"Sup." Inferno yawned from behind. I looked, and sure enough the little green Pegasus was sat, making a half-arsed effort to look interested in anything. "Nice wound. Corrosive?"
"Probably..." I whined, getting back to my hooves and looking at the wound. A huge patch of flesh had completely, and violently, disintegrated, before being cauterized with a strange green substance. It hung in small clumps of my fur, before corroding those. Sadly, I watched my fine blue fur die in a patch of corrosion.
"Ok." Thunderlane said as he landed from his locking of the manhole. "We have the whole town hunting us, and no doubt will they find a way down here. One of us is seriously injured by something that looks like acid, deadly acid at that, and all three of us are wanted colts. Fun frickin' times." he groaned, stomping a black hoof on the floor.
"Yeah," I spoke carefully, so as not to aggravate my condition. "Probably not the best idea to send, or write, that letter."
"Letter?" Thunderlane asked, ruffling his wings in confusion.
"Yeah, Inferno wrote a letter about who was snagging, or courting, who, and then Spike sent it to Celestia."
"Pfft."
"Anyway, we can sort it out in Canterlot. Right now, we need to find an easy way there that doesn't involve my wound opening whilst my blood goes everywhere."
"Hmmm..." Thunderlane asked, looking at my wound and tapping a hoof to his chin. "I ever tell you I went to medical school?" he asked.
"No, you didn't." I replied.
"Because I never did go. I think that we ought to see the doctors up in Canterlot. They'll know what to do." Thunderlane gestured to a tunnel leading into the darkness. "Let's go that way."

"Yep." Inferno sighed, standing up and trotting down the route. He seemed uninterested in what was occuring: maybe he was stoned?

The roars came back. They would, I knew they would. Those room-shakingly loud Thresher roars that haunted you for life. Thunderlane seemed perfectly fine. How could thou be so fine when Terry hath returned to thine Pandora? I trotted to keep up with the black Pegasus so that I didn't end up lost here.
"You hear those roars?" I asked.
"Yep." replied Thunderlane. "Already heard 'em. That's why I know a shortcut; through the underground caves beneath Canterlot."
"Mmmmm..." I quietly mused. "Isn't that where Cadence was...?" Suddenly, he stopped us, stepped forward, and stood beside a lever.
"Here we are: my hidden entrance." Thunderlane proudly claimed. He gave the switch a sharp tug, to which the lever squealed in protest, before finally a loud chugging was heard. I braced against the ground.
"Do you have some kind of map in your head?" I shouted as a nearby wall receded into itself, folding until another path was visible.
"Almost," he replied, casually backpedalling into the tunnel, "My father took me down here as a foal. He worked here, until it closed down. Come on, lemme show you some of the stuff they left behind. It's on the path, after all!" he grinned. I smiled back, and followed him through, followed by Inferno. As we went through the tunnel, I noticed some familiar objects imbedded in the walls. Hammers, axes, pickaxes, and as we went further in, the temperature dropped rapidly. "Just keep goin'." Thunderlane shivered. I listened, and carried on looking at the ice walls. Frozen in time were fossils, even one fully frozen pony, looking confused as to why he froze. I also saw a few chests, some more familiar than others.
"Wow." I shivered, just as we left the area and entered what appeared to be an elevator. "This thing still work?"
"Course." Thunderlane replied as he opened the fuse box. His hooves seemed incredibly fluent with the fiddly wires, and after some cursing, smacking, and banging, the lights flickered to life in the wooden carriage. "Probably gonna be slow though. Ever seen an ancient elevator that's powered by electricity rather than a hoof-crank?"
"Nah." I replied. "Why? We gonna be attacked by Terramorphus?"
"Hopefully not." Thunderlane muttered as the lift clanked into life and began its slow ascent to the surface.