The Grand Plaza of the Vault bathed in twilight's glow as the Festival of Unity reached its zenith. Lanterns crafted from bioluminescent corals drifted through the vaulted ceilings, casting dancing reflections on crystalline walls. Delegates, warriors, and civilians alike mingled beneath banners of the Dawn's Edge Concord, celebrating a momentary reprieve from conflict.
Julius Reyes stood near the Forge Seed's chamber, Seraphel hovering by his side, watching the festivities with a mixture of pride and caution. Music from distant holo–instruments floated through the air—a blend of Navis string harmonies, Terran percussion, and Hollow Kin chants.
"Everyone seems so… hopeful," Brinley murmured, clasping a warm cup of fermented spore–wine. He gestured toward laughing children playing under projected starlight. "It's nice to see."
Vara joined them, her glaive strapped to her back. "Hope is our greatest weapon. We just have to hold onto it."
Seraphel's glow pulsed gently. "The Forge Seed's resonance remains stable. But I detect a faint, persistent pulse far below the ocean's bed—an echo not wholly extinguished."
Julius felt a familiar tension uncoil in his chest. "Again?"
Seraphel nodded. "The ripple emanates from the Polaris Trench—deeper, older, more primal than any Hive nest. The Source's hinterlands."
Brinley's grin faltered. "So it's back to another deep–sea dive?"
Vara exhaled. "Seems our work never ends."
---
A Call Beneath the Waves
The party at the Vault continued, but a panel of Vanguard command convened in the inner council chamber—a circular hall with holo–displays tracing the Expanse's hidden tracings. Lia Vrissa, flanked by Admiral Kiriath and Captain Vorn, listened as Seraphel's projection outlined the echo's location.
"The Polaris Trench extends six thousand kilometers," Seraphel explained. "Deepest point lies at seven hundred atmospheres of pressure. Visiting it requires specialized craft and knowledge."
Admiral Kiriath's blue hands tapped a nav chart. "We can reroute supply vessels, but we'll need Abyssal–class submersibles retrofitted with symbiotic shielding."
Captain Vorn nodded. "Ironclad Hold has blueprints for those. We can build them here—two weeks' work."
Selene interjected. "Meanwhile, we track the echo's growth. If it seeds another hive or worse, an entity—"
Ryka's voice cut in, eyes steely. "We move now. Gather what we can. If this echo becomes sentient… we need to be present, not reacting too late."
Julius stood. "Agreed. Assemble a strike team: Seraphel, Brinley, Vara, and me. Selene and Ryka can coordinate the fleet's movements and civilian evacuations. Kiriath—advising on nav support. Vorn—prepping submersibles."
Lia Vrissa gave a crisp nod. "We cannot ignore the Source's beckon. I'll call for volunteers, but it'll have to be a small, experienced cadre."
Seraphel's form brightened. "I will guide the tracers. We will enter the trench and uncover its origin. Once there, we decide whether to purge or parley with what remains."
Julius felt a chill, remembering the Architect's volatile promise. "Then let us be ready. The Vanguard stands as one."
---
Journey to Polaris
Two days later, the Vault's dock bristled with construction: hulking blue Abyssal submersibles lined up like silent leviathans. Smith–engineers from the Ironclad Hold welded symbiotic plating onto each hull, while Vesper Pact technicians integrated Scout AI modules for autonomous navigation.
The night before launch, Julius paced the Launch Bay, Seraphel's glow dim in the dim emergency lighting. Vara approached, adjusting her wrist console.
"You rest," she said. "I'll take first watch."
He stopped. "You rest, too."
"Not when the Source calls," she replied softly. "We owe the Vault—and every world we protect—our vigilance."
Brinley ambled over, a flask in hand. "Here. For bravery." He offered a swig.
Julius accepted a drink, nodding. "To the Vanguard."
They sat in silence, watching the submersibles' silhouettes under crimson spotlights.
"Launch in twelve hours," Seraphel's voice echoed in Julius's mind. "I will prepare recon protocols."
Julius tapped his symbiotic implant. "Understood. And… thank you, Seraphel."
Her glow brightened faintly. "Stay alive. Hold fast to hope."
---
Descent into Darkness
When dawn's violet rays crept across the Vault, four submersibles glided into the ocean's swirling surface. The Vanguard strike team—Julius, Seraphel, Vara, and Brinley—watched from observation hatches as the vessels disappeared into the rolling waves, leaving frothy trails of disturbed water.
Two days later, the adapted submarines breached the Polaris Trench's outer depths. Darkness swallowed them. Their scanners displayed jagged contours—cracks in the planet's crust that exhaled geothermal heat and swirling bioluminescent currents.
"We're at 10,000 meters," the sub's navigator reported. "Hull integrity nominal."
Selene appeared on the sub's holo–comm. "The Vanguard fleet holds orbit. Any sign of cataclysms on your feed?"
Julius glanced at Seraphel's slowly adjusting readouts. "All calm. But sensors detect the echo's pulse converging at 20,000 meters."
Brinley flicked on an infrared array. "Visual feeds—nothing visible. But the trench walls… they're alive."
Indeed, the walls glowed with drifting motes—ancient symbiote sculptures, half–grown architecture melding rock and code. The deep waters hummed with frequencies making their suits resonate.
Seraphel's voice whispered in Julius's mind. "Be prepared. This trench was once the forging ground of the Nexus. Now it hosts the Source's impulses."
Suddenly, the sub quaked as something brushed against its outer hull—massive, unseen, ancient.
Vara's voice crackled over comm. "Julius—brace! Something is coming."
The sonar spiked. A deep pulse echoed—a structured pattern like a heartbeat in the abyss. Then the walls convulsed—massive plates shifting. The sub's lights revealed a colossal chamber ahead: a cathedral–sized gorge veined with living glyphs, each script in continuous flux.
At the chamber's center lay an immense crystalline prism—its facets refracting deep blue luminescence. The echo's origin. The Source's seed.
Brinley swallowed. "That's… unreal."
"We dock," Julius said. "And finish this."
Seraphel rose, tendrils flickering. "I will forge the resonance."
As the sub glided into the chamber, the water stilled. From the prism's facets rose an echoing pulse—a calling that resonated deep within each Vanguard member's soul.
Outside, in the infinite ocean of space, the Vanguard's beacon shone bright—ready to heed that call and stand at the Source's final crucible.