Crossover Shipgirls: Building a Dimensional Empire from Scratch

The empty-nester Bone King was now panicking.

Fighting a player one-on-one or a guild war in a game was one thing. An interdimensional war was something else entirely.

The war declaration spelled it out clearly.

The other party had declared war on the Great Tomb of Nazarick.

This was a fight to the death. The war wouldn't end until one side was utterly annihilated or surrendered.

The victor could seize everything from the loser.

"A PvP with the objective of complete annihilation and item looting for the group..."

Ainz fell deep into thought.

He tried to interpret the current situation using his gaming knowledge.

He wasn't afraid of pure PvP. Back in YGGDRASIL, with cash items and god-tier gear, he could 1v2 players of the same level.

Group battles were more troublesome.

As a magic caster, Ainz habitually gathered information about enemies beforehand, tailoring buffs and strategies accordingly.

Fire attribute enemy? Stack fire resistance. Holy attribute? Stack holy defense, and so on.

But now, he realized he knew absolutely nothing about Setsuna and the Starsea Empire.

Their level, magic, class—warrior, mage, rogue, or something else—was a complete mystery.

"Engaging without intel is very disadvantageous..."

He held his skeletal head in contemplation.

"My Lord, all fools who dare offend the Supreme One and Nazarick should be utterly destroyed."

Demiurge looked up and declared.

"Since they've already issued a war declaration, they clearly won't back down."

"We must make them feel the deepest fear and pain—as punishment for offending the Supreme One!!!"

"Hmm..."

Ainz nodded and looked at the floor guardians:

"What are your thoughts on our enemy? I'd like to hear your opinions."

"Lord Ainz is invincible!"

"Just a bunch of low-tier lifeforms!"

"How dare lowly humans challenge Lord Ainz? Throw them to the torturers and the horrors!!!"

All the floor guardians were diehard fans. Filled with hostility toward the outside world, they didn't regard the enemy as a threat at all.

"..."

The ever-calm Demiurge paused, sensing Ainz's concern.

"Lord Ainz, you need not worry. Judging by appearances, the enemy seems to be human."

"Those inferior beings are no match for us."

He smiled elegantly and confidently.

As undead and high-tier demons, they naturally had pride in their identity and regarded humans as insignificant.

It wasn't just racial arrogance—this view was backed by detailed investigation.

Humanity's overall strength in this world was far below that of other species.

The strongest human mages could only cast up to 6th-tier spells—not even strong enough to beat a single Pleiades maid.

The mightiest warrior captain would barely stand a chance against a summoned creature Ainz could casually create.

From a combat power perspective, humans had a low upper limit—completely outclassed by Nazarick's undead and demons.

"Is that so..."

Ainz relaxed a little.

After his first communication with Setsuna, he had thoroughly investigated the surrounding region.

Though he hadn't found the target, he did manage to map out the power systems of this world.

Humans were generally low-level. While legends mentioned top-tier figures like Antilene, they were few in number—nowhere near enough to challenge Nazarick.

Suzuki Satoru had been human in his previous life. But after coming to this world, he had grown accustomed to his undead identity and new way of thinking.

Humans were just inferior creatures.

He could wipe them out with a wave of his hand.

"Very well."

After a moment's thought, Ainz spoke gloomily.

"Cocytus, I order you to be the vanguard and confront the invaders from another world."

"I will provide necessary support."

Considering the risks of personally facing an unknown enemy, Ainz decided to send a strong floor guardian first to test the waters.

He would observe the situation from Nazarick using magic.

"Yes, Lord Ainz!"

A towering insectoid warrior clad in pale blue carapace bowed his head in acknowledgment.

Standing upright on two legs with four arms for weapon wielding—

Cocytus, floor guardian of Nazarick's Fifth Underground Floor, the strongest in melee among all NPCs.

Ainz placed great expectations on him.

"I will not disappoint you. I shall slay those foolish invaders."

...

More than an hour later—

Several hundred kilometers from the Great Tomb of Nazarick,

Cocytus stood tall on the plains, wielding a silver halberd in one hand and a divine-grade katana—Zan Shindao Emperor—in the other.

Behind him stood hundreds of neatly aligned Death Knights, exuding an ominous aura.

Any adventurer stumbling upon this sight would collapse in fear, nearly suffocating.

These figures—draped in rags, wielding swords and shields, surrounded by black mist—were apocalyptic threats to the natives.

The Empire could barely suppress even one or two using its full might. For Nazarick, they were summoned effortlessly.

Next to the Death Knights stood platoons of skeletal warriors clad in golden or silver magical armor.

Countless other undead troops filled the area.

The stench of decay they emitted was already corrupting the plains into a dead zone.

Ainz and the other floor guardians remained in Nazarick, observing through magic.

Only minutes remained before the world gate would open.

He was deeply curious—what kind of enemy would emerge?

"As expected of the Supreme One, deploying Cocytus to meet the invaders."

Demiurge continued his mental acrobatics, interpreting it as a grand plan.

"Cocytus ranks among the top-tier guardians. If he defeats them, they will surely grasp their foolishness..."

"Even if he loses, we'll uncover their weaknesses and strike decisively..."

"..."

Ainz internally muttered: I'm just uncertain and probing their strength.

But he still nodded seriously.

"A sound analysis, Demiurge."

They exchanged a few more words.

Buzz—

[Interdimensional Passage Opened]

As the countdown ended,

The sky twisted.

The passage between Earth and the Overlord world was now fully open.

"They're here!"

Ainz unconsciously gripped his staff, and the guardians gathered beside him,

Nervously watching the magical projection.

On the ground, the rulers of the Holy Kingdom, the Empire, and the Re-Estize Kingdom all looked up.

"Following standard PvP logic, tanks and warriors usually charge in first to draw fire—don't get bogged down..."

Ainz explained his tactical philosophy to Cocytus via telepathy.

"Quickly locate and eliminate enemy magic casters and archers—especially mages. Take them out before they can activate powerful spellcasting tools..."

"Understood!"

Cocytus assumed a battle stance.

BOOM!!!

A violent shockwave shook the sky.

The first to emerge from the temporal rift was the towering hull of the Eternal Snowfall.

Its metallic prow pierced the clouds and blocked out the sun.

Though airborne, the ten-kilometer-long starship still cast a massive shadow on the ground.

Behind it followed carriers and battleships.

The fleet moved in orderly formation, emerging slowly from the passage and arraying in the air.

Destroyers and cruisers formed escort wings on both sides.

Being undead, the skeletons couldn't feel fear, but they instinctively looked up.

Cocytus, gripping his weapons in all four hands and preparing to charge into melee, raised his head to look—

And froze.

This... wasn't what Lord Ainz had taught him.

Who were the tanks? The warriors? Where were the mages and archers?!

"Lord Ainz, what is this?..."

The guardians had never seen a starship before. Even the most erudite Demiurge had no idea.

"Are those flying magical beasts?"

Shalltear blinked.

"Eh????!!!"

"Ah!!!!!"

Ainz gawked in disbelief, greenish-blue lights flashing across his body repeatedly.

Shoop—

Stand up. Sit down.

Shoop—

Stand up again. Sit down again.

His forced calm skill triggered seven or eight times within a single minute.

"What the hell is this?!"

"Star-destroying ships??!!"

"Why does something like this even exist??!!"

Ainz was convinced the game must've bugged out.

Back when he was alone in YGGDRASIL waiting for the servers to shut down, something went wrong.

The chat system and GM communication had already gone offline when—

He suddenly received a mysterious message from another world.

A man said, "Let's stop playing charades," and it scared him half to death.

He had dispatched NPCs to surrounding nations to investigate the source of that mysterious communication.

Naturally, they came back with no useful information.

After all this time, when everything seemed to have returned to normal—

The other party actually invaded on their own initiative!

And they brought a space fleet with them.

In Suzuki Satoru's previous life, he had never seen ships like these.

No warriors, clerics, or magic casters—the enemy brought star-destroying ships!!!

The floor guardians might not know what these things were, but Ainz understood very well.

They were absolutely players! 100% not native to YGGDRASIL!!!

But where did players even get spaceships? YGGDRASIL definitely didn't have that tech.

Ainz was utterly baffled.

"Why does your art style look completely different?!"

It was terrifying.

Shoop—

Shoop—

Shoop—

Watching Ainz repeatedly stand up and sit down,

With forced calm green light flickering wildly around him,

Demiurge, Albedo, Shalltear, and the others were thoroughly confused.

"Lord Ainz, what is...?"

Huff—

Huff...

After seven or eight forced calms, Ainz finally regained the ability to think.

He leaned back on his throne, taking a deep breath with his nonexistent lungs to settle himself.

The forced calm skill allowed him to control his actions during emotional surges and suppress inner anxiety.

His human fear gradually faded, replaced by the undead's reason and cold logic.

"The enemy could be very troublesome."

"They're also players."

"Hm?"

The guardians pondered this.

"You mean, like the other Supreme Beings?"

"You could understand it that way."

The NPCs in Nazarick had seen other players before. Their behavior was unpredictable and fundamentally different from game NPCs.

"Lord Ainz, why are they so different from the Supreme Beings we've seen before?"

Shalltear looked at the magical projection.

"Those flying metal blocks—are they some kind of flying magical beasts?"

She had no concept of spaceships and could only interpret them through YGGDRASIL's lens.

"..."

Ainz was speechless.

"Lord Ainz, what should we do?"

Demiurge asked.

"Hmm..."

After several rounds of forced calm, Ainz finally recovered from the shock and began to analyze the situation.

"Calm down. Calm down..."

"The enemy has spaceships and superior tech, but that doesn't mean they're invincible in this world."

"This is a world of magic. We can counter with magic and items."

He clutched the ornate staff embedded with jewels—

Guild weapon: Staff of Ainz Ooal Gown.

His inventory was packed with pay-to-win gear and world-class items, giving him a sliver of reassurance.

After all his comrades left, he hoarded nearly all the guild's equipment. Combined with his past as a heavy spender in the game,

Ainz had quite a few absurdly overpowered items on hand.

For example, among the so-called "Twenty" world-class items, he owned eleven.

These items severely disrupted game balance. They might just be capable of handling these absurd enemies.

"Let Cocytus probe the enemy's capabilities,"

Ainz ordered.

"See if they have weaknesses or resistances to piercing, slashing, magic, and such skills."

"Also, observe their attack methods. Cocytus, if you fall, I will revive you."

"Understood."

...

"So this is the Overlord world?"

Onboard the Eternal Snowfall, Gudako, Mio, and the others examined their surroundings.

Another fantasy world.

It resembled the Goblin Slayer world in many ways—

Medieval-style cities, forests teeming with monsters.

Overall low technological level, but magic was clearly prominent.

In a world where magic could do almost everything, it was understandable that humanity hadn't pursued tech.

Why bother with steam engines when you have Flight and Teleportation?

Just let the mages handle things.

"Oh, is that Bone King's welcoming committee?"

Setsuna noticed the undead army below.

Led by Cocytus, the Death Knights, skeletal warriors, and lich archmages stood in neat formation on the ground.

"Ugh, so many people—"

The Butterfly Sisters and Akame shivered.

There were thousands of undead below. They knew they weren't a match for these things.

The big blue bug leading them looked especially dangerous.

The average combat power of the Overlord world far exceeded that of the Akame world.

"Is that some sort of spell that raises the dead to fight? That's just disgusting. Ugh."

"I can practically smell their stench."

Jeanne Alter spat in disdain.

"Fools who dare invade Nazarick, state your names!"

As everyone was sizing things up, Cocytus drew his sword and shouted skyward.

"..."

The starships gave no response.

"Attack!"

Cocytus swung his silver halberd forward.

Whoosh—

Behind him, dozens of robed, decayed mages stepped forward.

Holding twisted staves, their rotten faces held evil wisdom. Though gaunt and skeletal, they radiated great magical power.

Lich Archmages.

Roughly level 30. In the original story, one nearly wiped out the Lizardman tribes. Among the undead army, they were standard forces.

Boom, boom, boom—

The mage formation hurled over a hundred blazing fireballs at the starships above.

The fireballs exploded against the energy shield, causing ripples and sparks.

[Klein Field Saturation: 0%]

"That's it? Weaker than mass-produced angel missiles."

The attacks were so feeble that Setsuna couldn't even get a reading.

He glanced at the control panel.

Little fireballs like these were no different from pebbles.

Seeing the fireballs ineffective, the liches switched to lightning bolts, ice spikes, and other elemental spells.

Soon, the sky was filled with crisscrossing spells of fire, ice, and lightning.

"Fire!"

With Cocytus' command—

Skeletal archers aimed at the starships and released a volley.

Unlike native archers, their weapons were enchanted, with range and power far exceeding normal.

Many were cursed or poisoned.

Bang bang bang—

The arrows shattered upon impact with the energy shield.

"Completely immune to low-level magic and piercing..."

Ainz muttered grimly.

Still within expectations—

Anyone with the guts to invade worlds wouldn't be stopped by fireballs.

He was increasingly curious about these starships. In YGGDRASIL terms, what level were they?

Even if they were technological constructs, they should still have a tier.

Unfortunately, under magical projection, he couldn't read their stats.

Scouting personally was too risky. Ever cautious, Ainz chose to wait and see.

"Annoying."

Setsuna was growing irritated with the constant barrage of fireballs and lightning.

He waved his hand.

Clack—

A turret beneath the Eternal Snowfall locked onto a target.

Buzz... BOOM!

After a brief charge-up—

A dark-red energy beam slashed through the sky, as if tearing it apart.

The super-graviton cannon descended at light speed, striking the ground.

Cocytus didn't even have time to raise a defense.

Nothing can react faster than light.

Upon impact, massive energy detonated, swallowing the Death Knight core.

The resulting shockwave spread out—

Skeletal warriors, lich archmages, even their enchanted armor were vaporized in an instant.

Those nearby were scorched into bone dust. Those farther out were torn apart by the blast.

Cocytus lasted only a few seconds longer.

His body disintegrated under the high-energy beam, and even armor comparable to legendary items couldn't resist.

"Lord Ainz... my apologies..."

When the dust settled, only a thousand-meter-wide crater remained.

The previously organized undead army was reduced to ash.

"..."

Ainz stared, stunned, at the magical projection.

On the adjacent interface, Cocytus' name was crossed out in red.

Each guardian's death triggered an alert.

"Lord Ainz, this..."

The other guardians were also in disbelief.

"Super-tier magic!!!"

"Ahhhhh!!!!"

Ainz slammed the table, triggering several forced calms again.

To destroy a floor guardian in one hit—

The starship's firepower was undoubtedly equivalent to super-tier magic.

Even stronger than Fallen Down!

"Damn, are our enemies using super-tier magic as basic attacks??!!"

...

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