After clearing out the swarm along the coast, Shiomi brought Artoria and headed with Ereshkigal to the nearby observation station by the Persian Gulf, while Quetzalcoatl returned to Eridu to assess the situation there.
The station, once bustling with activity, was now completely deserted. The area outside and atop the tower was littered with damaged, mangled corpses, and the inside was in total disarray.
There, Shiomi reestablished contact with Chaldea.
"From here, the view is clear. A crimson tide is steadily spreading across the distant waters of the Persian Gulf. And there are more of those creatures in the sea—similar to the ones we just fought," Shiomi said, brow furrowed. He gazed at the part of the sea not yet tainted red. More of those lifeforms were surfacing, though they hadn't begun to move yet.
They were likely newly spawned—still dull in their senses.
But it wouldn't be long before they turned just as vicious as the earlier ones.
"For convenience, let's name those mass-produced lifeforms Laḫmu," Romani said seriously. "Judging from the situation, the black mud staining the Persian Gulf is most likely one of Tiamat's Authorities—'Chaos Tide.' Neither humans nor Servants should come into contact with it."
"Tiamat's Authority…" Shiomi murmured, lips tightening.
"Let's make one thing clear—neither your power nor the Holy Lance Goddess's can compare to my mother's," Ereshkigal warned. "Sure, you can foster life in the Underworld, but even that requires your own blood as a medium."
"Your tiny spark of life-based Authority is nowhere near the level of Mother—of Goddess Tiamat's—power. She has self-modification, individual replication, and life-fusion. It's on a whole other level."
"I know… She's a creator goddess." Shiomi wasn't arrogant enough to deny it.
Besides, he'd always rejected the idea of ascending to the Throne of Gods. There was no way he could compare himself to the Origin Goddess.
"As I mentioned earlier, the most terrifying of Mother's life-based Authorities is 'Amino Geas.' Once you're swallowed by the black mud, it's over," Ereshkigal said grimly. "No matter who or what you are, you'll be eroded and become an enemy of humanity."
"And ever since the Holy Grail was taken, the rate at which the black mud is corrupting the sea has accelerated—by the minute," Romani added. "Soon, the SHEBA observation mirror won't be able to monitor anything. We'll have to rely entirely on you all over there."
"How much time do we have?"
"Based on the judgment provided by Assistant Officer Gilgamesh—at most, three hours," Romani answered. "After that, the observation station you're in will be consumed by the black mud. The black sea will rise onto the land and eventually swallow all of Mesopotamia."
"This is worse than the Great Flood of Utnapishtim that once drowned Mesopotamia."
"Three hours…"
Shiomi gripped the wall atop the observation tower and stared into the depths of the sea.
Tiamat was out there. But even with his vision enhanced to its magical limit, he couldn't see a thing.
"There's more…" Romani hesitated.
"What?"
"We've detected a massive Spirit Origin reaction above the Persian Gulf. Its mana output exceeds the combined total of all seven Holy Grails. It's an ultra-class Magical Energy Core. We believe it to be the Spirit Origin of Tiamat—the primordial Magical Beast that gave birth to Mesopotamian civilization."
Romani's voice grew increasingly tense.
"So, if we can defeat Tiamat's true body, this black sea will vanish?" Shiomi asked.
Ereshkigal looked startled. "Defeat Mother?! Do you even realize what you're saying?"
"The Axe of Marduk is here. If I stake my life on it and try again, maybe we can kill the awakened Tiamat." Shiomi pressed a hand to his chest.
"But Master, your body still hasn't recovered from the last time you used it," Artoria said.
"But this time, we've got the Goddess of the Underworld and the Sun Goddess on our side. Once Quetzalcoatl returns from Eridu, we'll ride the pterosaur and head out to sea to intercept Tiamat," Shiomi said. "Unless... the two of you don't plan to join this fight—in which case, I'll figure out something else."
Ereshkigal quickly responded, "I-I never said I wouldn't help! Besides, if Mother really steps onto land and lets the Black Sea engulf Mesopotamia and its civilization, the foundation of humanity will be completely destroyed!"
In other words, she had no choice—nor could she turn a blind eye.
"Then it's settled. I'll lead Artoria, alongside both goddesses, to intercept Tiamat—"
Before he could finish, Morgan's voice suddenly broke into the transmission from Uruk.
"In that case, I'll come immediately."
"No." For once, Shiomi cut her off without hesitation.
"My husband, are you planning to charge in alone? Do you really think I'll just stay behind in the rear and be safe?" Morgan asked with a hint of displeasure.
Shiomi took a deep breath. "Intercepting her at sea is a high-risk operation. Considering the low chances of success, if we confirm it's not possible, we'll retreat at once. At that point, your... uniqueness might become the trump card against Tiamat. Please start conserving your strength now and prepare for that moment."
His words caught everyone by surprise. No one had expected Shiomi to say that—much less with such certainty.
But before anyone could say anything else, Morgan gave a knowing smile.
"I see... So that's what you've been planning. Then I'll follow your lead, my husband, and stay in Uruk to hold the line with the others. But—"
"But?"
"Send Scáthach instead. If someone has to stay behind and face death, let it be the woman who can't die." Morgan said it almost like a joke, then added seriously, "It was her own request—and she's already on the move."
Shiomi, who had been about to argue, suddenly fell silent.
A trace of melancholy passed through him.
Whether it was Morgan, his mentor, or Artoria, they rarely clashed with him.
But they all had strong wills of their own. None of them would stay in safety just because Shiomi thought the situation was dangerous.
Unless… he could present an alternative plan convincing enough, like the one he'd just given Morgan.
"Master," Artoria said, taking his hand.
"We've still got some time before Quetzalcoatl returns. Let's rest first. I haven't fully recovered yet, and Artoria's used her Noble Phantasm twice in quick succession," Shiomi said to Ereshkigal. "So I'm leaving surveillance of the Persian Gulf to you for now."
"Don't sleep too deeply. I won't have time to wake you up if something happens," Ereshkigal replied casually.
With that, Shiomi took Artoria's hand, and the two of them disappeared into the observation station.