Even with Lucia's immense magic power from defeating Finis, constructing the devices was grueling work.
To activate a magic circle, five different spells had to be channeled into it simultaneously, requiring intense concentration. Each time a magic circle was activated, the vast reserves of magic power were depleted in an instant, and fatigue began to interfere with what had been flawless magical control.
It would have been helpful if Selen and the members of Star's Holy Thunder could assist, but each mage had their own specialty. The magic circles for the devices required five spells to be channeled in, and among those, the fire spell had to be a considerably powerful one.
While simultaneous activation alone might have been manageable, Spiritfolk were naturally disadvantaged when it came to fire magic. Selen couldn't use fire magic at all, and among the members of Star's Holy Thunder, only Kruse Argan could.
However, there was no shortage of work. Instead, Selen and the others took on the task of processing gems into magic stones that would serve as the devices' power sources.
Without a power source, the devices wouldn't function. This work also required delicate magical control, though perhaps not to the same degree as the devices' construction.
By the time Lucia had used up all the glass Citry and the others had gathered, and Selen and the rest had completed their initial processing of the gems, the sun had long since set.
Everyone, including Selen, was exhausted from the nerve-wracking work. The only one still in top form was probably Citry, who had been directing operations.
Yet, her expression was far from dark. Because there was hope.
That single victory — rescuing Luin, a victory that seemed like nothing more than sheer coincidence — had invigorated Selen and the others.
Right on cue, the team members who had been surveying the device installation sites returned.
Riesz, Elisa, and Tino — the three thieves who had completed Luin's retrieval via the Dog Chain and then ventured back outside Yggdrasil to conduct their investigation — along with Adler's group, who had been monitoring their progress through the Scrying Glass and marking everything on maps.
Even without a threat on the level of Finis, it had been a perilous mission; other Phantoms could have attacked at any moment. But Riesz's trio had no notable injuries.
Riesz's expression, however, was grim. Lucia, who had been squeezing every last drop of energy into the device construction and was now barely breathing, furrowed her brow and called out.
"...Welcome back. Did something happen?"
"No... There weren't any Phantoms attacking today, and no particular trouble either, but... we were being watched the whole time. It was creepy as hell."
"...We felt their gazes. Right from the moment we entered the forest, all the way through —"
Tino shuddered, her shoulders trembling.
They had already suspected heavy surveillance the moment the barrier was erected, but this was the first time they had actually felt being watched. This was not a comforting development.
How things would unfold was beyond even Selen's ability to predict. But the situation was undoubtedly moving — not just for Selen's group, but for the Origin Temple as well.
Riesz clicked her tongue and spoke irritably.
"So, just to check, we went all the way near the Origin Temple, and they were just standing there behind the barrier, staring at us. Those black-masked Phantoms — we tried provoking them, but they wouldn't come out. And the barrier has no seams, so we couldn't get in either... Pisses me off."
"You went that close, huh... Hmph. Same as always."
"You gotta get close to figure things out! Ugh, those eyes... so damn annoying! If Luke were here, maybe he could've cut through the barrier, but he's nowhere to be found when we need him!"
At Lapis's words, Riesz threw a glance her way and kicked the ground in frustration.
Though surely even a swordsman of Riesz's caliber couldn't simply cut through a barrier formed by spatial severance — Finally, Elisa, who had been wandering about with a drowsy look on her face, let out a soft breath and spoke.
"They seem to be holding back for now, but they're watching to see what we do. From the looks of it, if anything happens, they'll attack immediately."
The Phantoms of the Origin Temple were powerful. Luin and Finis had been recovered, but hundreds of Yggdrasil's elites had also gone missing.
Yggdrasil's fighting force was still incomparably smaller than that of the Phantoms.
As if confirming Selen's anxiety, Citry furrowed her brows and made a troubled expression.
"Well, well... this has become troublesome again. After activating the devices, it takes time for the effects to manifest. And on top of that, we have to activate multiple devices simultaneously."
Right. The strategy was still only at Phase 2 — the preparation stage.
"Well, we won't know until we try, right? Adler, you lot, try to be at least a little useful!"
"As if we would — well, actually, we get it. I suppose we should show at least some value to Thousand Transformations, shouldn't we?"
Adler said with a cruel smile.
Thinking of Klye, she tried to imagine what the future battle might hold. But she couldn't read it at all.
Selen knew nothing. She didn't know what the Phantoms were thinking, how many existed, how great their fighting force was. And — what Yggdrasil's current forces could even accomplish.
Battles were subject to the whims of fate. And for even the Spiritfolk, who possessed abilities surpassing those of humans, controlling the flow of battle — let alone predicting the outcome — was impossible.
Klye Andrich still showed no sign of appearing.
Where was he, and what was he doing? Or... was everything still going according to plan?
"Big Sis Elisa... if I may ask a rather bold question... aren't your feet wanting to run away?"
"...They've been wanting to run away the whole time. This is a losing battle. If you think about it normally, that is. That's how vast the gap in fighting strength is."
"!? ...I-I see... so it's that kind of fight again after all..."
"But now that we've come this far, there's no running. We place our bets on Citry's devices, and everyone who can fight has to protect them to the last."
Elisa, wearing an unusually grave expression, spoke to Tino, who had slumped as though deflated.
Selen had suspected as much, but apparently even from the perspective of these seasoned thieves, the odds weren't looking good.
But as Elisa said, regardless, they had no choice but to press forward. For Selen and the others, this was their last chance to redeem the dishonor of failing to stop the World Tree's rampage.
What they had to avoid above all else was the Mourning Specter descending upon them. If that happened, even if Star's Holy Thunder remained on their side, nothing could be done.
The cooperation of Thousand Transformations was essential above all else. Selen checked each face in turn and spoke with as much dignity as she could muster.
"I too... despite being a princess of Yggdrasil — my combat experience is limited, but if I borrow Miles's power, I should be able to fight even the Origin Temple's Phantoms. And once Luin wakes, he should fight alongside us as well."
The Mourning Specter had come here to save their comrades. But whether it would be easier to break Shero's curse or to stop the World Tree's rampage — that didn't even require consideration.
Reading Selen's expression, Citry allowed herself a small smile.
"You don't need to worry. We won't step down — at least, not until Klye decides to withdraw. But — Uno, have you figured out the state of the ley lines?"
"Yes. It's rough, but I believe I've been able to check the points where the ley lines intersect. There shouldn't be any major oversights. When it comes to investigation, nothing beats using people rather than the Dog Chain."
Uno spread out a map of the surrounding area. The map, centered on the World Tree, now had several red lines drawn across it.
These must have been created by tracking Riesz and the others through the Scrying Glass as they walked through the forest.
Citry took the map and compared it with the one Selen had handed over — an old map from Yggdrasil's archives.
"It roughly matches the five-hundred-year-old ley line map you gave me, Selen."
"This is only after circling the perimeter once, so I've managed to capture the main ley lines, but I can't guarantee completeness. After a few more rounds, I should be able to produce a more precise map."
Selen knew nothing about the principles or requirements of the Mana Material Agitation Device.
Even if Yggdrasil's technology surpassed others in this area, the people of Yggdrasil had never entertained the audacious idea of redirecting ley lines.
Citry thought for a few seconds, then shook her head.
"...No. For now, let me calculate the installation locations using this data. We've been given a valuable opportunity to verify. If you and the others were being watched, then time is short. Selen, please do share your input as well. The fate of the world hinges on whether this works."
§ Once again, she received an explanation of the device at the heart of the operation.
The Mana Material Agitation Device.
As its name suggested, it was a device designed to disrupt the flow of Mana Material.
Citry compared the ley lines to rivers, Mana Material to water, and the devices to obstacles. Using the Mana Material Agitation Device, one could obstruct the flow of water and gather more water at a single point than would naturally accumulate.
Mana Material didn't flow as smoothly as water, and there were slight differences in properties between the ley lines and the devices, but the key point was that the device had originally been designed to disrupt the smooth flow of Mana Material and increase the amount of Mana Material at a single location — to strengthen the Treasure Hall.
Citry Smart was using the properties of Mana Material and the devices to attempt to bifurcate the river known as the ley line. It was an unprecedented strategy, feasible only in theory.
"Ley lines are the pathways of Mana Material. If we could artificially create new paths for Mana Material to flow through, those could legitimately be called ley lines — like digging a river channel to create a tributary."
In Yggdrasil, Mana Material flowing through ley lines was repurposed to power various spell formations. The powerful barrier surrounding Yggdrasil was one such application, and the construction of the World Tree's cycling paths relied on it as well.
Compared to the human world, where research into Mana Material was restricted, their technology was likely more advanced.
Selen had heard the general function of the Mana Material Agitation Device. Citry's proposed strategy didn't seem impossible from Selen's perspective either. However — "Well, we've strengthened things before, but we've never weakened the Treasure Hall. But it should definitely be possible. In theory!!"
Citry clenched her fist and spoke passionately.
Lucia had been incredible for continuing to fight against Finis, who possessed overwhelming power, but Citry Smart was something else entirely.
After all, in this situation where the end of the world was staring them in the face, she was about to attempt a use of the device that had never been tried before.
And now Selen understood the reason Citry had not explained the strategy's details until now.
She must have waited until the point of no return.
She had kept saying "in theory." This was unquestionably an experiment.
Moreover, the installation locations for the devices were extremely difficult to determine. Citry had said "if installed in the right positions," but it was questionable whether such ideal positions even existed.
Ley line structures varied from place to place. In other words, device placement had to rely on rough heuristics, and there was no way of knowing if things would work properly until they actually activated.
Selen had agreed to the strategy, but she hadn't expected it to carry this many uncertain variables.
And even in an emergency, Thousand Transformations — who had (presumably) understood all of this and handed everything over to Citry — were remarkably composed.
In front of Selen, whose face had gone taut, Citry spoke forcefully, as if steeling herself.
"Trust me! In theory, it will work!"