[FATE] OP Demon King Across Multiverse!

Deep within the Ryūdōji Temple, Artoria Pendragon, clad in jet-black armor, slowly opened her glowing golden eyes.

She could feel it—they had arrived.

The red markings streaked across her face pulsed with a sinister aura, an unnatural distortion of her once-noble presence.

Meanwhile, Ryuu caught up with Mash, Ritsuka, and Olga, giving a quick explanation before stepping into the temple's inner sanctum—

The heart of the Greater Holy Grail.

The moment Ritsuka laid eyes on it, they felt a chill crawl down their spine.

"What… is this…?"

The massive Grail loomed before them, swirling with corruptive, violet energy.

Even Olga Marie, a magus born into nobility, gasped in shock.

"This… isn't just a Holy Grail—it's a supercharged magical furnace!"

Ryuu remained silent. He already knew.

He scanned the area—Artoria had to be here.

And, sure enough—

A cold, regal voice echoed from above.

"Master… it seems you've brought a new group of warriors with you."

They all looked up.

Standing atop the Greater Grail, Artoria's corrupted form exuded overwhelming magic power.

The blackened Holy Sword hummed in her grip, its cursed energy radiating into the air.

Ryuu smirked.

"Saber… long time no see."

Mash gripped her shield tightly.

"She's the legendary King of Knights… I can feel the overwhelming strength in her magic!"

Since their last battle, Artoria had grown even stronger.

But Ryuu was no longer the same warrior either.

Even so, he knew—if they fought one-on-one, he still couldn't win.

"Is she the Servant of your new contract?" Artoria asked, gazing at Mash. "She looks weak."

"Sorry, Mash isn't my Servant," Ryuu replied.

Artoria tilted her head slightly, a faint smirk appearing.

"Is that so? Then, unknown girl—why have you come here?"

Mash stepped forward without hesitation.

"To resolve this Singularity—and restore human history!"

A glint of amusement flashed through Artoria's golden eyes.

"Oh? Then, let's see if you're worthy. Servant of the Shield—let this sword test the limits of your defense!"

Before anyone could react—

A black sword swung downward.

Mash barely managed to raise her shield in time, the force of the impact shaking the entire cavern.

She gritted her teeth and countered with a shield bash, but Artoria easily dodged.

Even so, a flicker of surprise crossed the corrupted king's face.

"Your Spirit Origin is weak," Artoria murmured. "Yet you blocked my attack… Interesting."

The sheer shockwaves from their exchange sent Ritsuka and Olga stumbling backward.

Thinking fast, Olga activated a magic stone, forming a protective barrier around them.

"Why aren't you helping?!" Olga shouted at Ryuu. "Mash can't fight Saber alone!"

Ryuu smirked.

"Relax. This is something she needs to experience."

"You…!" Olga gritted her teeth.

But as much as she hated to admit it—she couldn't deny his words.

Artoria continued her onslaught, forcing Mash onto the defensive.

"Is this all you can do?" Artoria asked, striking relentlessly. "You won't even attack? Are you waiting for someone to save you?"

Mash clenched her fists, remembering Ryuu's words.

(If you hesitate, you'll die. If you're afraid to act, you'll never grow stronger.)

She refused to retreat.

"Ugh…!" Mash gritted her teeth, holding her ground.

Ritsuka tried to step forward, but—

"Stay back."

Olga blocked them with a sharp glare.

"But Mash—!"

"If you interfere, you'll just get in her way."

Ritsuka froze.

"If you were as strong as Ryuu, I wouldn't stop you," Olga added. "But right now—you're not."

Ritsuka bit their lip, unable to argue.

(…I can't do anything yet…)

Meanwhile—

With a final, crushing blow—Mash's shield wavered.

Her knees buckled.

The force sent her crashing onto the ground—her shield slipping from her grasp.

Artoria slowly advanced, black sword poised to strike.

Mash struggled, crawling forward to retrieve her shield.

Her body screamed in pain, but she refused to stop.

"Ugh… I won't… let it end here…!"

She reached for her shield—

But the corrupted holy blade was already descending.

"Not today."

CLANG!

A massive shockwave erupted—

Ryuu blocked Artoria's sword with his Rebellion blade.

A flicker of relief passed through Ritsuka and Olga's faces.

"Finally!" Olga exhaled. "With him fighting, we actually have a chance!"

And yet—Artoria simply smiled.

"I knew you would step in," she said calmly.

"Of course," Ryuu replied. "But I'm not fighting alone."

"Hmph. You mean that girl?" Artoria glanced at Mash. "If the one wielding that shield were him, then perhaps there would be hope."

Mash forced herself to stand, gripping her shield tightly.

"I won't back down."

Artoria's smirk faded.

"…Very well. Prove it."

For the first time—Ryuu and Mash fought together.

Ryuu's Third Blood Awakening activated.

His Rebellion Blade pulsed with magic.

His Geass-infused eyes tracked every movement.

Artoria clashed head-on with Ryuu, the cavern shaking with each impact.

Mash provided defensive cover, blocking Artoria's strikes at key moments.

Their coordination was flawless.

Sometimes, they attacked together—forcing Artoria onto the defensive.

Other times, they staggered their assaults, preventing her from finding an opening.

Even Olga and Ritsuka watched in awe.

(Their synchronization is… perfect!)

Despite their overwhelming teamwork, Artoria still held the advantage.

Her blade movements were precise—each strike carving through the air with lethal intent.

She wasn't struggling.

If anything—she was enjoying this.

SLASH—!

Ryuu barely dodged in time, but Artoria's blade grazed his waist.

For the first time, a wound appeared on Ryuu's body.

He gritted his teeth—but smiled.

"Finally…" he muttered.

Mash widened her eyes.

"Mr. Ryuu, you're—"

"I'm fine," he interrupted. "We're just getting started."

The two warriors reset their stance.

The corrupted king raised her sword once more.

"Come then," Artoria challenged.

"Show me if you're worthy of this fight."

The battle continued.

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