With nothing else to do Celestia lay in her bed, tired, nervous, but finally not hopeless. Even if they still had to actually accomplish their plan, the fact that everypony agreed on it and seemed mostly hopeful restored her own faith as well. Yet, as much as she turned and twisted, sleep evaded her, an unending, dull reminder of her sister’s absence.
With a groan, she got up and stepped to her window. It was hard to see through the clouds illuminated by the ghost-light of the enchanted crystal lamps, but she eventually managed to make out the mirror image of the Moon below, which meant they were already over the sea. It was all very peaceful, just endless gentle waves of water below, crested by the soft creaks and rumbles of the airship.
Still, she felt a sense of unease, one whose origin she couldn’t exactly pinpoint. She supposed it was due to the mission, but it felt different somehow. Just then, the rain began to fall from the clouds above, obscuring the image of the Moon. The loud pitter-pattering as the drops began to beat against the window shook all tiredness from her eyes.
She sighed and turned from the window, choosing to venture out of her room instead of continuing to languish inside. She figured perhaps stretching her legs would allow her the rest she so desired. Not wishing to disturb any rooms where others were surely already asleep, she decided to climb the staircase connecting the cabins to the engineering deck out of curiosity. Passengers technically were prohibited from entering the deck, but she also was the monarch of Equestria and the primary financier of the project, so surely she would be forgiven a little curiosity.
Unlike the welcoming wood-covered corridor of the cabins, engineering was a lot more utilitarian and bare. Metal corridors with low hoofrails ran up and down the tight hole between the envelope of the ship and its gargantuan gas balloons, which hung above like great cocoons in the half-light of the hull. Though ‘tight’ was perhaps an overstatement, as due to the size of the Lux Aeterna even its utility gaps were big enough for an alicorn like herself to comfortably walk in them with her head held high.
“Halt! Who goes there? This is a restricted area!” a stern, yet familiar voice called out towards her, quickly followed by the light of an oil lantern.
“Hello, Heavy Wrench,” Celestia called out with a snicker. “I’m happy to run into you here.”
“Wha- Your Highness?! Up here?” Wrench asked in shock.
“Indeed. Are you perhaps insinuating that the princess may not tread where she pleases?” Celestia replied with feigned offence, before dropping the act and laughing into her hoof.
The mare shifted nervously on her hooves, clearly in trepidation about what to do. “Technically... you can’t,” she finally muttered, eliciting another chuckle from Celestia.
“It’s alright, I’ll be very careful and I promise to cause no issues. Especially with you next to me.”
“Please forgive me but I cannot accompany you, Your Highness. I was making my way towards the engine, it’s the start of my shift. Almost everypony else is asleep by now.”
“That’s alright,” Celestia said with a wave. “I’ll accompany you instead, then.”
“I... don’t think...”
“Please?”
Hearing her monarch actually ask made Wrench both awfully proud of herself and a little bit ashamed that she tried to be such a stickler for protocol, when there wasn’t any chance that Celestia would cause any trouble.
Heavy Wrench sighed heavily. “Very well, Your Highness,” she finally said. “Please follow me.”
The two mares made their way down the winding corridor, their path lit only by Wrench’s lamp and the occasional dim luminescent crystal hanging from the hoofrails every couple dozen metres or so. They remained mostly silent through the walk, the quiet broken only by the soft hum of the machinery which the cabin’s thick padding had filtered out before.
Every once in a while the duo stopped and Wrench pointed at something she helped build or design. For a pony that lacked wings, she was entirely in her element in the air, her natural confidence further heightened by her years of experience tinkering with the various flying machines sailing Equestria’s skies. Wrench nodded towards a set of tubes running high up into the upper half of the ship. “That’s where inputs from the gondola to inflate or deflate the balloons goes through.” Later, as they were passing a slightly brighter crystal, she pointed at the faintly visible frame of the ship which provided the structure for the gigantic envelope. “We had to design it to be both as light as possible whilst also being capable of holding so much weight. There’s pegasus magic imbued inside, the three tribes can make really fancy things together, isn’t it so, Your Highness?” she asked and Celestia beamed back towards her with a wide smile.
“It is very much so, my little pony.”
After some more trotting, the pair finally reached into the engine room at the back of the airship. Six stocky rows of giant crystal-batteries surrounded a tube-shaped machine. The moment they entered Celestia immediately began to feel the immense power stored inside as a dull throb in her horn. She grimaced and raised a hoof to it. There was another feeling too, a far more violent and chaotic magic, but she couldn’t exactly figure out what it was. It dulled her senses and for a moment she nearly lost her hooves. Almost like brain freeze, she thought, but that’s ridiculous.
Wrench rushed in front of her. “Oh my apologies, Highness! I forgot to tell you this shift is only filled in by earth ponies. Unicorns are unable to comfortably work in this environment. If you’d rather go back to your quarters...”
Celestia rolled her shoulders and stepped deeper inside. “No, it’s fine, the pain has already passed. It was just unexpected.”
“V-very well.”
The engine hummed loudly next to them as the force of the raw magical current was captured and turned into angular velocity that drove the giant rotors of the ship. Barrels of oil stood in one corner of the room, used to fuel the non-magical lamps found on the ship. “Each of these rows is capable of producing the magic of five-hundred unicorns,” Wrench explained. With a few ballpark calculations and seeing the amount of crystals along with the pressure she was feeling in her horn, Celestia figured it was unlikely she could muster anything more than a few seconds of concentrated magic capable of matching this sort of output.
“Hmm, from what I can see”—Celestia looked around the room—”the engine seems to be working just fine alone. What exactly do you have to do here?”
Wrench stepped deeper inside and began to walk between the rows of crystals, occasionally gently tapping her hoof against one or listening to their hums. She spoke as she worked, “I still don’t suppose this will be very exciting for you, Highness, but mostly my job is to just inspect the crystals for structural stability and to make sure the connection between them and the engine is stable.” She reached the end and stepped into another row. “Routine work, really. While an earth pony isn’t attuned to unicorn magic, our ears are keen enough to make out the different tunes that crystal resonance makes without the, well, less than desirable effects of the method of storage on our minds.” She gently tapped the battery next to her. “The timbre allows you to precisely estimate the crystal’s output and status,” she looked to meet Celestia’s eyes. “And believe me, Highness, a faulty crystal’s tune is one you don’t forget for a long time.”
Celestia followed her and began to listen to the crystals herself. Though she wasn’t a trained engineer, she had both earth pony and unicorn magic at her disposal. As she listened, everything seemed fine, only... “So, as I was saying, poke the crystals a few times, listen to their timbre, simple job really. Truth be told I was only really told to come here and do it myself because of that little cargo mishap. Very sorry about that, Highness. It was an honest mistake,” Wrench babbled on whilst Celestia tried to concentrate.
“Shh,” she suddenly said, causing the engineer to quickly fall silent.
“Huh? Is there a problem, Highness?” She tipped her head to the side. “I can’t really hear anything wrong.”
“The power draw feels too strong,” Celestia whispered. Wrench’s eyes slowly grew wide as she began listening earnestly herself.
“That’s... Yes. Yeah, it’s very faint, but it does sound a bit stronger than usual,” Wrench listened for a few more seconds. “You have a truly exceptional ear, Your HIghness. Still, it’s probably not a problem.”
Celestia raised a brow. “Probably?”
“Well, we might just be making a manoeuvre, or perhaps there’s a bit too much drag, or...” Wrench’s monologue was suddenly cut short, as the previously dull hum of the crystal climbed to a piercing whine. “A faulty crystal,” she finished with the blood drained from her face. “This isn’t good at all.”
Suddenly the crystal flashed. Time seemed to slow as Heavy Wrench’s eyes lazily turned towards the crystal which burst into a million fragments in slow motion. She closed her eyes and waited for impact.
It never came. The engineer slowly opened her eyes. In front of her, like snow inside a snow-globe, the crystal’s many shards glimmered against a pale-yellow shield. Still in shock, she slowly looked to her left. Celestia stared back at her panting, another shard-covered shield drawn in front of her.
“We must report this to the Captain at once,” she stated flatly.
“Y-yes, Highness.”
The two ponies raced back to the bow of the ship and quickly climbed down into the gondola.
Inside they found only Captain Sky and the coxswain Steady Hoof. The rest of the ponies were likely on break or asleep.
“Oh, Princess!” he greeted Celestia warmly, before turning to the engineer. “And Wrench... How pleasant,” he added with less warmth in his voice, still feeling sour over the cargo fiasco. “What do we owe the visit?”
Celestia didn’t waste time greeting him back. “Captain, the engines are drawing abnormal amounts of magic. One of the crystals has already blown. I am not willing to endanger my subjects any further, we must land at once.”
Sky tipped his head to the side, confusion written on his face. “Forgive me, Highness, but I’m not entirely sure what you’re talking about. While it is true that we’re about to head into a storm and flying through those requires a bit more power, we haven’t measured anything that could cause worry.” He pointed behind himself, where one of the gauges labelled ‘Magic Output’ was showing a steady level, far below red. “See? This machine is almost perfect, it has not dipped below or risen above that level for hours. Smoothest machine I’ve ever flown,” he said with a confident smile. “You have plenty on your plate, please leave these things to your subjects.”
Celestia’s face darkened as she listened to him. “Don’t you understand? She was nearly eviscerated by one of the crystal-batteries. Her only luck was that I was present,” she said, pointing to the still-shivering Heavy Wrench.
“Still, Highness, the levels are fine.” Sky gulped nervously. “We check them every five minutes as per protocol.”
Celestia stepped closer to the gauge, making the captain awkwardly move out of her way as she looked at it. The base of the needle seemed wrong somehow. She leaned even closer. The detail that caught her attention was very subtle, but as she moved her head, she saw a glint. It was like the machine was...
“This is frozen!” she almost shouted. Not wasting any time, she melted the ice with a bit of her magic and the needle immediately sprang deep into the red, almost breaking in the process. “How long has this been showing the wrong value?”
“What?” Sky’s mouth hung open as he read the new value. “That cannot be, this-this is way too much power!” He spun towards Steady, forcing some composure on himself. “Wake the crew, all hooves on deck! Prepare to switch to temporary non-powered flight, the engines must be taken offline and restarted,” he rattled off. Steady saluted and darted up the stairs.
“Go with her and help,” Celestia told Wrench, who followed immediately.
“I... My apologies, Your Highness. This is my fault entirely.” Sky nervously fiddled with his hat. “There is not much we can do at the moment until I get the crew. The ship was not designed to fly without its engine, so there is no method of turning it off from here. I also cannot lower the speed, we need all the momentum we can get to weather the reboot,” he explained to Celestia, before turning to the gauge. “I don’t understand! Who could’ve sabotaged our machine? I’ve been on watch almost the entire day and whenever I had to leave, Steady was here to mare the post.”
“Perhaps it wasn’t sabotage then,” Celestia replied gravely.
“What else then, Highness? This is a heated room and our instruments are behind glass. What if not magic could have caused the ice? I have seen heat generated by faulty instruments before... but ice?”
The princess glanced outside where the previously thin blanket of clouds had since become an impenetrable dark curtain, split by lightning and thunderous rain. “There is one explanation...”