There was more to do. On Nashido there always was. The sky kingdom was blocking sunlight on the starboard side, and the moss was dimming in protest. Kio and Karla spent several hours dragging mirrors around to charge the moss with sunlight so the castle wouldn’t plunge into pitch darkness at nightfall.
The vines were parched too. It hadn’t rained for the three days they had been holed up in the hangar. The largest ones had vast stores of moisture in their tissue, and didn’t mind much, but the smaller, newer ones had paper-dry bark and disconcerting brown spots. So the two humans drank from the mist garden, and the half-rebuilt aqueduct was set aside for the oxygen vines.
“Why do plants have to die anyway?” Karla grumbled, sprinkling precious water on a bed halfway up the northern hemisphere of Nashido, which she’d climbed out the window of an Outer Citadel bedroom to reach. She knew plants had life cycles–the great vines that produced most of the oxygen for the crystal-maintained atmosphere had once been thinner around than her arm. Still, it didn’t seem fair.
“Are you thinking it’s not fair?” Kio called up. He was leaning out the window, ready to catch Karla if she fell off the series of gears she’d climbed up to reach the curved soil bed.
“Well it’s not.” She dripped more water from a can with holes battered in it. “When they’re around whole systems of plants, they die so they can feed the others. But we have one closed system. It would be so much more convenient if they could just live forever.”
“Those are just the rules, Karla.”
“Why do the sky and earth and middle have to follow the same rules?”
“They don’t always,” Kio said, probably thinking about runes.
Karla’s can ran out of water. She gingerly handed it down to Kio, trying to ignore the rough cut of metal on her wrists. Vines themselves were much easier to climb, but they didn’t go everywhere–Nashido’s perfectly fitted stones were partly covered with gears large and small whose purposes they could only sometimes determine. Their best guess for the ones on the bedroom towers was some kind of dumbwaiter.
Vaulting in through the window as Kio dodged aside, she decided it was high time they built drip irrigation for the smaller soil beds. Another thing to look for up in the sky kingdom.
She looked up, on instinct, but only saw a stone ceiling. Kio squinted at her.
The vast floating island had kept pace with them all morning–or Nashido had followed it. When the sun was out, it cast its shadow over the reservoir, the kitchen and storerooms, the hunting platform and observation towers and the aft-jutting machine deck lower down. When clouds closed over them, like they were right now, the kingdom remained barely visible as a speck half-wreathed in the world of gray.
It loomed over their conversation, too. Unless Karla was angry about plants or Kio was uncomfortable with the direction Karla was pointing something sharp, they were talking about how to get to the sky kingdom.
“We keep coming back to the same problems,” Kio lamented, as they worked on opposite sides of a water catchment pod, screwing it down to the one large girder they’d salvaged from the aqueduct. “All twelve kingdoms we’ve explored so far have been on a level with us. We could zipline from our highest point to their flatlands, and then run another line back to our lower half.” His wrench slipped, and he looked over the pod at her with a fretful expression. “Do you think it’s because of rune decay?”
Karla decided they wouldn’t gain anything from pursuing that. They were going to find what they needed, and until then, there was no use worrying.
“I’ve been thinking about runes, actually,” she said instead. “I have a theory.”
“What is it?” Kio attacked another bolt.
“It’s about what the big runes do.” She had her side finished, so she scuttled around to help with is. “You know what gravity is, right?”
“Force exerted by objects with great mass on objects without it,” Kio grunted. “The number one rule the sky kingdoms and Nashido have to break to exist.”
“Yeah. But I’ve been thinking about how they break it.”
Kio paused his work to stare at her. “You solved magic? Without even going into the library?”
“Being in there hasn’t helped you much,” Karla retorted. “Listen for a second. If you know gravity, you know there are some important characteristics of being without it.”
“Zero gravity, yeah. There’s no force biasing motion one way. So anything you do will exert a reaction in whatever direction it wants, unopposed.”
“I mean, I read about friction–“ she paused for a second, but Kio didn’t seem surprised “–but that helps us. In space, we’d just keep going forever.”
“Hang on. Helps us do what?”
“That’s what I’m getting at. I think those big runes aren’t propping Nashido up, necessarily.” She leaned closer and pushed hair out of her face. “I think they’re making the castle behave as though it’s in zero gravity.”
Kio brushed his face tattoo absently. “Sure. Maybe. But you still haven’t said what we’re supposed to do with this information.”
“Think, Kio!” Karla laid into the row of bolts again, tightening the cloud-catcher down to the girder. “The propellors push air behind us to create forward thrust. We need–“
Comprehension exploded like a firework onto Kio’s face. “–to let out a ton of force downward to create upward thrust.”
“Maybe more than a ton.” Karla finished the last bolt and happily inspected her work. “But yup. That’s the idea.”
The triangle of three observation towers had different gears than the living keeps: big ones that Kio theorized had belonged to a telescope which had broken off at some point, with belts of tanned hide running between them. They’d repurposed these to hoist and lower the aqueduct, but it was still a bit of climb to get where they needed to be to lift the girder back into place. While they climbed, and then while they hauled, they shouted ideas at each other about what they could jettison to launch up toward the sky kingdom.
“There’s always cabbage,” Karla called as she mounted a platform with a spear turret, halfway up from the reservoir.
“Enough with the cabbage. I like cabbage,” Kio shouted back. “Besides, if we had a ton of any kind of food we wouldn’t need to shoot birds for months. Or spreading our own dung on things.”
Karla shuddered enough at the thought of months of cabbage that she was sure Kio could see from all the way across the chasm.
The great girder, with its big cloud-catcher pod fixed to its center and ropes tied to either end, lurched up the space between the towers in fits and starts. In the dark gray light, it looked like some kind of knife-edge mountain ridge on one of the surface islands, being pushed upward inch over inch by some exhausted god. As Karla hauled, she looked over its crisscrossing struts, appreciating what she’d done to get this here. Glad that she’d placed it, and would place it again, even though she hadn’t made it.
But there were other things we didn’t place at all…
Her hands froze on the rope. Kio yelped as he took a much greater share of the strain. “Sorry!” she yelled to him across the gap, and then, once they’d leveled out the beam: “I know what to jettison!”
“You’re sure about this?” Kio asked, because he wasn’t.
“Absolutely,” Karla replied, pretending she was. Kio chose to be reassured anyway, which in the end wasn’t very reassuring.
They’d worked late into the afternoon, and now rested amid a darkening sky with no sunset to be seen. A band of moss spread across the walls of the outer citadel gave off a warm light.
They were standing on what, if the machine deck was aft and the hangar forward, would have been the starboard side of Nashido. The mist garden clung to the port side, founded on giant single slabs riveted together by the carved ends of support pillars. Balancing it on the other side was a balcony with a staircase up to an outer citadel hallway. A door on the other side of the balcony led into the only residence tower on the castle that pointed straight down. It was a quiet spot, sheltered from the ever-present wind, with one of their vegetable gardens in the corner of the veranda. Kio really hoped it would remain quiet when they twisted the tower in exactly the right way to drop it clear seaward.
“You’re sure the math is right?” Karla asked.
“Are you? You double-checked it.”
“Yeah, but I want to hear you say it.”
“Why?” Kio leaned back on the balcony rail, tried to look nonchalant, failed.
“Because you like to be sure of things. I like getting to the doing things part. So I trust your math more.”
Kio was mostly busy making sure their balcony really was attached by its own pillars that wouldn’t fall off, but he found the courage to nod. “I’m sure.”
He shivered in his layers of fur, feeling the crinkle of the dozens of torn-out pages he’d stuffed into his pockets. There were formulas in ancient ink plus his own calculations in smeared charcoal. He’d never found blueprints of Nashido in the library, not for lack of searching, but he had found information about the building style the cut and fitted stones copied. All the posts bearing the weight of the hanging structure had slotted ends carved to fit with similar slots in the stone floor of the inner citadel. On their own, the poles would never budge. With just the right push, however…
Kio’s eyes traveled up to the base of the two-story bedroom tower, which they’d encircled with rope. The far ends of all the ropes were lashed to their source of torque: the two great propellors. And what had they run the ropes through to ensure they’d apply force in the right direction?
He laughed a bit, probably out of fear. Gears. Ridiculous Rokhshan gears. He didn’t even have a theory about these underside models. But that didn’t matter. They were useless no more.
“Ready?” he asked Karla.
“Let’s go,” she said. They scuttled up through the doomed bedroom, into the hallways.
On the machine deck, she revved the engine to ensure it still had power. They’d dismantled the lightning rod extensions to rebuild the aqueduct, and it would be an enormous hassle to refill the battery–but the engine turned over the first time. Karla shot Kio a look, and chuckled a lot like he had on the balcony. “No more excuses.”
“Just do it.” Kio’s stomach turned.
Karla nodded, checked her hair was tied back, and threw the lever forward.
He leapt at her. “Slower! You’ll rip the props off!”
She throttled back, quieting a terrible whine and screech from right below their feet. But the louder, deeper sound, the grind of stone on stone, continued.
It happened all at once. One second, Nashido’s outline looked like it had been for ten years, like it had been for all of Kio’s life. The next moment, for the first time since he’d known where he was, part of the castle was falling away. The ropes bound around the tower twisted it, then shoved it, the grinding growing loud enough to drown out the wind. The low tower slid free of its moorings, released its grasp on the balcony, and tilted.
Once it was free, it fell so quickly Kio thought there must have been magic involved. As though Nashido’s exception to gravity had been suddenly revoked on that tower, yanking it hard out of the castle’s sphere.
The ropes jerked taut, then went slack as they lost their load. The propellors went gratefully quiet. Kio turned away and covered his eyes with his arm, leaning against the instrument panel Karla was working. She laid a hand on his shoulder, kept throttling back with the other. “It’s all right,” she said. “We got everything useful out.”
“It’s not that.” Kio gritted his teeth. “We’ve never lost any of it before, Karla. We’re supposed to be the guardians of Nashido.”
Only after the words were out did he realize how Rokhshan he sounded. “We’re supposed to protect ourselves,” Karla replied. “We’re making a trade. One tower we don’t need for–“
Her grip on his shoulder tightened. “Kio, look!”
Against his will, he did.
In the gray evening sky, it was difficult for any milestone to show how fast they were moving. The only way to tell would be by the sky kingdom itself, the tiny speck of–
Not a speck anymore.
Kio stumbled to his feet. Karla shut the propellors off hard, whooping with joy. The sky kingdom was growing, expanding to fill the arc of sky they could see. In seconds it was the size of the tallest towers of Nashido from where they were. A minute after that, they were close enough to see ruts and furrows of rock on the underside, along with–Karla grabbed Kio’s arm and pointed it–amazingly large lifting runes carved into them. Their light was faint, and some old ones were dead. But channels of glowing energy ran between the others in a net of power as beautiful as a sky full of stars.
Their scheme had worked. They were going to the sky kingdom.
They were also, Kio reflected later, looking entirely the wrong direction for what came next.
It was not until he heard the roar that Kio realized what a bad idea it had been to launch something off the castle, that day, when the clouds were too thick to see anything coming at them. Somehow, the dragon must have been able to pierce the veil. For anybody who could see to the horizon, the tower they dropped into the sea would be a beacon shone out to miles around. Come and get us.
The bone dragon sailed up through the clouds, gaining form as it went, pounding its silvery wings. It might have been the same one, rebuilt, or it might have been bigger. By the time Kio noticed it, he was beyond thinking of such things.
One final wingbeat flipped the dragon in midair, head down, eyes glaring right at them. With a hiss that shook Kio’s own bones, its talons slid into the gaps the tower had left behind.
Karla shouted his name from somewhere far away. The dragon’s fiery eyes turned, its tangle of legs splaying over the citadel’s surface. It wasn’t looking at them anymore.
Kio knew as surely as he knew gravity worked most of the time. The dragon wanted Castle Nashido.