Iron Shod had become far more aggressive since they had tricked him into injuring himself. Since he had started to relentlessly drive Luna back down the hallway, the other ponies had decided that it might be too dangerous to attempt to pass him and had hidden in the newly opened cell.
This impression was aided by the fact that he had embedded the cell door in a nearby wall whilst trying to swing it as a weapon, forcing him to revert to the plentiful supply of wooden benches lining the wall.
A magical blast from Luna shattered one of Iron’s projectiles, but opened her up to an impact from another that had thrown her halfway down the hall. Galloping up to her, he attempted to bring his metal talon down on her head, but she rolled to the side at the last moment and he struck the stone floor with all his strength.
He yelled in pain and stumbled back, holding his forelimb close to his barrel. Luna wondered why, but on closer examination she noticed a sharp, bloody metallic point protruding from his elbow.
He attached the prosthesis with a stake, she realized. Not the smartest thing perhaps, but I shudder to think what some stallions won’t do to establish and maintain a tough image…
Breathing heavily, Iron Shod looked up at the princess with an expression of pure hate on his face. Setting down his limb, he began to limp forward, an aura of magic holding his quarry’s hooves in place. He grinned nastily, and jumped at the princess, another wooden bludgeon clutched in his magic.
Then he shouted in surprise as a hoof-sized stone sailed over his head and struck him on the horn, stunning him for a fraction of a second, but more importantly causing him to lose his grip on the magic holding Luna in place.
Behind them, Luna sighted Rarity standing in the hall with a second stone in a magical grip.
Luna took advantage of Iron’s momentary lapse in concentration by dropping to the ground and firing a bolt of magic at Iron as he passed overhead. This gave the leaping pony much more height than he had counted on, hurling him over Luna altogether and into the windowframe that neither had realised they had approached. He flailed for a moment on the edge and toppled over.
Slightly dumbstruck, Luna approached the window, looking out over the vast expanse of the valley far below. And then she looked down to see Iron holding onto a stone ledge just below the window with both his intact hoof and talon effigy.
He had a wild, panicked look in his eyes, looking down and then back up at the Princess. “Help me!” he called.
Luna raised her eyebrows. “You want me to help you?”
Iron gritted what remained of his teeth, and immediately winced in pain. “I hate heights, okay? I won’t fight y’ if y’ help me up, I’ll let ya go, whatever.”
“Were I in your position, you would let me fall.”
“Maybe. I don’t know. But I'm not, so what does that matter?”
Luna stared at him for a moment.
“It matters because I am not you. Not anymore.” She reached a hoof down and grasped his prosthetic talon, attempting to pull him up.
“Thank you,” sighed Iron, only to be interrupted by what Luna would later describe as a ‘squelching’ noise.
His prosthetic, now supporting his entire weight, had given up the fight to continue doing so and had simply separated from Iron’s stump.
There was a moment of frozen panic before gravity took hold and sent Iron plummeting from the underside of the city with a scream.
Luna pulled herself back into the window and tossed aside the slightly bloody metal claw, trotting back towards the other seven ponies.
“We must leave quickly, before anypony else comes.” Everypony followed her upstairs, the fillies sitting on their older sisters’ backs.
Meanwhile, the fight against Cogspin was rapidly devolving into a stalemate, as Twilight maintained her shield and Cogspin hurled bolts of electricity at it.
“He’s right, I can’t keep this up forever,” said Twilight, her voice somewhat strained. “Anypony have any ideas?”
Poison mumbled something indistinct, still only half conscious. Celestia shook her head, and Pinkie simply glared at Cogspin.
“You can’t win!” he shouted. “That contract you signed was thorough and specific. ‘Neither Celestia nor any being who considers himself, herself, or itself allied with her may inflict harm upon the body of Cogspin the Greater or any who serve him.’” He threw another bolt, and Twilight visibly winced. Pinkie, however, looked thoughtful.
She reached a hoof into her mane and came out with the red stone from the hallway. Twilight’s eyebrows knit. “Pinkie, when did you get that?”
“I just picked it up. Thought it might be important. And if that was exactly what the contract said then it sounds like yes.”
Cogspin paused. “You can’t hurt me. No one can.”
“Are you sure?” asked Pinkie. “Because the contract said we couldn’t harm your body, and your body is out there. While this is… What is this? Soul? Mind? Essence of being? Either way, I feel like you should be more careful with your wording.”
Despite being incapable of facial expression, Cogspin suddenly seemed to grow nervous. “Give me that!” he shouted, giving up on the bolts and throwing himself at the shield. To no effect – he rebounded off of it like a stone against a shark tank.
Pinkie hoofed the crystal over to Celestia. “Here. You can decide what to do with this.”
Celestia looked at the piece of crystal. It cast a red glow over her face. “You have crossed a great deal many lines in the seven months of your kingship, Cogspin. I see no alternative but to put an end to it.”
Cogspin stalked around the magic bubble, his eyes on Celestia the whole time. “You would think that, wouldn’t you.” He levitated a piece of dull purplish-blue crystal from a receptacle on a pillar. “This is a communication crystal. I made some preparations as soon as my intruder detection spells went off. Can you guess who I’m about to contact?”
He plunged the crystal into the floor at his hooves, and it seemed to diffuse into the marble. A shimmering pool of light sprung up around it.
“Iron!” called Cogspin into the pool of light. “How goes your preparations?” There was no response.
“Iron! Where are you?” Silence.
“Iron, you respond to me this instant or so help me-” At that moment he was interrupted by a sickening crack, and the pool of light morphed into a cluster of jagged stone spurs. Exactly what was displayed on the rocks was hidden to the ponies in the bubble, but it caused Cogspin to immediately fall silent. His face was (of course) impassive as he removed the crystal from the ground and cast it away across the floor.
“Has your contingency plan fallen through?” asked Celestia.
“One of them,” said Cogspin, his voice perfectly modulated. “What of Aurora? If I die you will be incapable of freeing her from her prison.”
“Not true. I have access to some of the greatest scientific minds of my generation. It may take us slightly longer, but I have waited nearly a thousand years. I can wait a few more.”
Cogspin made an odd grinding sound, accompanied by a motion that Twilight associated with nervous swallowing in organic ponies.
“I had hoped that I wouldn’t need to resort to this, but you’ve forced my hoof, Celestia.” He reached up and snapped off his brass horn, revealing a hollow space underneath. Allowing the horn to roll away, he extracted something about the same size as the horn beneath which it had been hidden from the cavity and held it up to them. It was some form of metal structure, formed into a double helix and studded at regular intervals with faintly glowing white crystals. It was capped at both ends with a metal ring and seemed to produce a glow from within.
“Anypony with even a basic magical technology education should be well aware of what this is.” Cogspin held it against the bubble shield and the point of contact began to turn bright white, with tendrils spreading out across the shield like a cancer made of light. As this happened, the light within the object seemed to pulse.
“A helical converter,” stated Twilight.
Cogspin nodded. “I am the only thing keeping it stable right now. I’m sure you’ve read about the unfortunate tales of Bright Spark, Glimmer Stone, or Shining Nova, correct?” He didn’t wait for confirmation. “I have succeeded where they failed, but it requires constant maintenance from me. If I am no longer present to keep it stable, if for example, you were to kill me, then it would rapidly reach capacity and overload. And I’m sure I don’t have to tell you educated ponies about Marenobyl now do I?”
Celestia’s head drooped, and she lowered the crystal to the ground, where it rolled away. “You win, Cogspin. I will not risk the lives of so many of my little ponies.”
“There are many lengths to which you would go to destroy me, I should think,” laughed Cogspin, “but risking the destruction of Equulaneum? That is not one of them.” He charged another lightning bolt at the tip of the converter.
And then there was a crunching noise, and he froze. He, Celestia, Twilight, and Pinkie looked back to see Poison Point, clinging onto consciousness by a thread, her hoof surrounded by shards of red crystal.
“Eat that… you piece… of…”
Then her head dropped to the floor, and Cogspin screamed, a sound no normal pony could have produced, filled with metallic screeching and grinding. His glowing eye panels cracked and shattered, leaving darkness behind. And then he collapsed to the ground and ceased moving.
But their main concern was the helical converter, which had come to rest against the side of the bubble shield and was pulsing faster and faster.
“Twilight?” asked Pinkie. “This shield will protect us, right?”
Twilight never even had a chance to answer her question before a bolt of electricity broke free of the converter and arced over the shield, shredding it like tissue paper and converging on Twilight’s horn, knocking her unconscious. More bolts erupted from the pulsing gems of the converter, tearing across the stone walls of the throne room like knives through butter.
Celestia used telekinesis to drag Twilight, Poison and the verge-of-panic Pinkie Pie close to her, draping her wings over the three of them. A bolt from the converter blasted Cogspin’s abandoned body into shards of brass, which flew throughout the room and embedded themselves in various surfaces. Strangely, the Platinum Crown, still on Cogspin’s head when he had fallen, remained pristine. Celestia looked at it, the seeds of an idea forming in her mind.
And then there was a flash of white as the converter exploded.