Raiden Ei couldn't make up her mind.
But she had a trusty helper.
So she went to Reisen Riou, who was stimulating Makoto's soul, for advice.
She didn't voice her timeline convergence suspicions, instead saying she suspected Yae Saiguu was targeted by the Abyss with a subtle curse.
Her spellcraft was limited, so she'd found nothing.
"That tricky, huh?" Reisen scratched his head.
"Yeah," Ei nodded.
"So you want me to whip up another Sky-Veiling System?"
"Exactly," Ei said, nodding eagerly, all prim and proper.
The Sky-Veiling System could block Celestia's gaze, so it could easily shield against the Abyss, whose perception was far weaker.
"The Sky-Veiling System's data is locked in Revival's core. You can copy it there," Reisen said, still scratching. "Building it takes a ton of materials, and they're a pain to process. But a lower-grade version is easier. Good thing I didn't melt down the leftover tools."
"There's plenty of raw materials in the decorative storage. Check the special decor room," he added.
The Sky-Veiling System's main job was blocking world-level surveillance.
It couldn't use Teyvat-native materials, so it relied on Primogems and Genesis Crystals.
These were precious, but to Teyvat locals who couldn't process or use them, they were just pretty rocks, often decor.
Genesis Crystals: Crystallized energy of cosmic creation, born from the potential and hope to ignite new stars in the void.
Primogems: Primal crystals beyond this world, glowing with unclaimed dreams and hopes condensed in the dark cosmos.
Reisen had spent ages crafting tools to manipulate them. After tweaks, processing was decently efficient.
It was a minor detail, so he never mentioned it, and Ei never asked.
Ei clearly knew these materials. She first studied the Sky-Veiling System's hardware in Revival's core.
Then she grabbed raw materials from the decorative storage and hit the tool warehouse for processing.
Reisen watched her bustle, thoughtful.
"Ei's acting weird. My imagination?"
He shook off the thought.
Ei, meanwhile, found she couldn't forge Primogems or Genesis Crystals conventionally. She called Revival for tool tutorials.
"Didn't realize these things were so damn tough," Ei muttered. It took her over a week to replicate the Sky-Veiling System's hardware.
While the hardware and crafting were valuable, the system's true gem was its internal programming.
"Lord Ei, a reminder: the Sky-Veiling System's energy draw is massive. You'll need solid ley line crystals from the energy warehouse," Revival chimed in.
"Got it," Ei said, mid-replication.
She didn't need reminding—the system's energy demands were obvious.
She didn't need Reisen's stash either. The Shogunate's warehouse had plenty of solid ley line crystals.
Years ago, seeing Reisen hoard pure ley line energy, she'd suggested Makoto do the same. Makoto, ever indulgent with her sister, amassed a hefty stockpile.
Not as much as Reisen's, but about seven percent of his.
These crystals, manually compressed from ley lines, had no natural veins, so market supply was low.
If hoarding was an investment, the ley line crystal bet was a jackpot.
After Khaenri'ah's dark calamity polluted the ley lines, pure crystals went from pricey to astronomical, jumping from expensive goods to luxury status.
Before, a standard small solid ley line crystal cost about 100,000 Mora. Now? 900,000 Mora, and climbing, especially as nations battled the dark calamity. It was a strategic resource.
Before Ei's return, Reisen didn't know about the Shogunate's stash. The Narukami rituals and arrays used his personal stock.
The ceremonies were grand, but crystal consumption was less than Reisen expected.
No one had used solid ley line crystals at scale before, so their energy capacity was unclear. Reisen only knew they packed a punch.
Leftover crystals were still in shrine maidens' hands.
Reisen even sent a ship's worth to Liyue and Sumeru each, unsure if it helped, but it was a gesture.
This, despite constant battles and ongoing crystal use.
Soon, Ei finished replicating the software and programming.
She waved to a still-frowning Reisen, who looked ready to jump-start Makoto's soul with a lightning bolt. After checking Makoto's improving soul, Ei left the Serenitea Pot.
Without a word, she grabbed Saiguu and headed for a specially made secret chamber.
"Ei, what's this about?" Saiguu asked.
Ei couldn't spill the truth, so she reused the "Abyss curse" excuse she'd fed Reisen.
Ei had changed. The old Ei wouldn't have fibbed like this.
Now, she fooled everyone. Reisen had suspicions, but Saiguu, the fluffy-eared fox, bought it hook, line, and sinker, believing someone was out to get her.
"So, what's this thing?" Saiguu asked, eyeing a gleaming machine in the chamber.
The Primogem and Genesis Crystal device might not do much yet, but it sure looked impressive, catching the white-haired fox maiden's eye.