The Eminence In Shadow In Multiverse

But she was a Queen Piece.

Her master wasn't just a high-ranking devil but one of the Four Demon Lords' sisters.

Her choices couldn't be made lightly.

If Cid was too weak, then forcing her master to accept him as a servant would only cause trouble.

For now, it was safer to keep her distance.

She just had to make sure she didn't let things get out of hand.

"Tsubaki, you haven't eaten yet, right? Come sit and eat with me."

"Ah… Sure."

Wait.

When had she sat down?

And why was she holding chopsticks?

"Um…"

She quickly stood up, trying to make an excuse.

"I should go. I have another summon—"

"Relax."

Cid waved her off casually.

"I'm in great shape today. Better than ever, actually. I can more than cover the trade. Think of it as a vacation."

Completely. Unstoppable.

Tsubaki sighed.

"Just this once." (Next time, I'll keep my distance.)

But for now, she let herself sit back down and focus on their conversation.

"Remember what I said, Cid."

Tsubaki stood at the door, her usual sharp tone making a return.

"It's not safe at night. Stay home and don't wander around, got it?"

"Yeah, yeah. I got it. See you next time, Tsubaki."

Her shoulders stiffened.

"R-right. See you next time, Cid."

And as Tsubaki Shinra turned to leave, she couldn't quite shake the warmth in her chest.

Just this once.

Maybe.

….

Watching Tsubaki Shinra's figure fade into the magic circle, Cid picked up the now ordinary-looking flyer that had fallen to the floor.

He casually tossed it back into the drawer where it belonged, grabbed a bottle of milk from the fridge—courtesy of Eta—and downed it in one go.

Then, without so much as taking off his shoes, he collapsed face-first onto the bed.

"Both Natsuki-chan and Tsubaki mentioned something might happen soon.

Once could be a coincidence.

But twice?

That means something's definitely brewing."

He grinned.

"Sounds like the perfect stage for an Eminence in Shadow."

Three days.

That's how long he'd give it before heading to the academy to sniff out information.

For now, though—

Training.

A pure white crystal materialized in midair, floating silently beside his bed.

Cid took a deep breath.

"Inhale… exhale."

His muscles tensed, his entire body tightening as though bracing for an impact.

The Triple Compression Magic Refinement Technique.

An advanced version of the 24-hour refinement method he already practiced.

The core principle was the same—compress magic into his body while refining it to boost density and potency.

The difference?

This version operated at three times the pressure.

In theory, it was perfectly efficient.

It trained his magic circuits, muscles, and endurance all at once.

The cost?

• Intense physical pain.

• A constant feeling of being ripped apart and rebuilt.

• And a very real chance of dying if he lost focus for even a moment.

He'd considered maintaining the triple compression all day long.

But unlike the standard version, this one required his full concentration.

Letting his guard drop even for an instant would mean death. (Not ideal.)

Even so, as he endured the crushing pressure, Cid split a fraction of his consciousness and directed it into the floating crystal.

Inside the crystal, a projection of himself appeared within an endless white expanse.

He looked around at the blank space and muttered—

"Let's study fire magic today."

With that thought, bookshelves materialized from the void, stretching endlessly in all directions.

One by one, tomes of fire magic emerged—

Each one radiating an intense heat that would've burned lesser beings to ash just by being near them.

Cid called it the "Great Archive."

Or, more casually—"The Library."

The Library had appeared shortly after the world fusion.

It had approached him on its own—floating silently into his hands.

And now?

It served as his personal vault of magical knowledge.

Time worked differently here.

A single hour spent inside translated to just six minutes in the outside world.

And its contents?

Every spell and technique he had encountered from World No. 1 could be found inside.

Which meant—

If his guess was correct—

The Library wasn't just valuable.

It was one of the greatest treasures in existence.

When it first appeared, it had emitted strange sounds.

It took Cid weeks to decode those noises using its own records.

And in the end, the translation gave him only three fragmented words.

"Cross… resurrection… compatible."

"Seriously?"

He'd thrown the book he was holding at the time.

What kind of garbage translation was that?

No origin, no history, no user manual.

Just those three words.

And since then, no other clues.

But none of that really mattered.

Because after months of experimenting with the Library, Cid had to admit—

This wasn't just a treasure.

It was the treasure.

The three worlds all used different systems of magic.

• World No. 1 relied on "Mana"—an elemental force manipulated externally, ideal for mages.

• World No. 3 used "Magic Power"—a raw energy focused internally, making them close-combat specialists.

• World No. 2 blended both systems, but its top-tier elites focused on external manipulation.

Yet the Library bridged the gaps between them.

No matter how different the systems were, Cid found a way to integrate them all.

And now?

He planned to master every spell it contained.

As fire magic grimoires floated before him, Cid smirked.

"Let's get started."

The Eminence in Shadow always needed more tools—and more weapons—for the stage.

….

In theory, a person's magic type was something inherently fixed—something that couldn't be changed.

The only known way to alter it was through interbreeding with individuals from another world, producing offspring that combined the magical traits of both parents.

But the Library broke that rule.

It could change magic itself.

Even though Cid had technically discovered the method first and then used the Library to apply it, the knowledge had come directly from the Library's records.

And the scariest part?

It was contagious.

Take Gamma, for example.

She was the weakest of the Seven Shadows.

She never said it aloud, but Cid knew she was self-conscious about it.

Her lack of combat talent made her ill-suited for close-range battles—especially in the third world.

But she had an exceptional mind—perfectly aligned for magic combat in World No. 1.

So Cid's plan had been simple.

He'd give Gamma access to the Library and have her convert a small portion of her magic first.

Once converted, that strand of magic would act as a seed, gradually transforming the rest of her magic over time.

Simple.

Except—