Karl eased the submarine forward, thrusters whispering as they slid into the ravine. The walls closed in on either side—jagged stone rising like broken teeth, streaked with pale mineral veins that caught the sub's lights in brief, ghostly flashes. It felt less like navigating open water and more like threading a needle through the planet's ribs.
Agnes hovered near the forward viewport, her glow dimmed to avoid glare. "Careful here," she murmured. "The current funnels through this section. If you overcorrect, we scrape. If you undercorrect, we scrape worse."
Karl adjusted by a fraction, nanites flexing along the hull in anticipation. "You're saying scrape is unavoidable."
"I'm saying scrape is… negotiable," she replied, smiling. "This ravine wasn't designed with submarines in mind."
"Rude of it," Karl muttered.
They glided deeper. Pressure crept upward—not enough to alarm the reinforced hull, but enough that Karl could feel it, like the ocean's hand pressing against his spine. The demons were gone now, crushed or scattered above, leaving only the deep and the stone and the low hum of systems.
"…Hey," Karl said after a moment. "Random question."
Agnes turned toward him. "My favorite kind."
"The Mariana Trench," he said. "That's… here, right? Pacific?"
She blinked once—then laughed softly. "You're not dumb, if that's what you're worried about. Yes. The Mariana Trench is in the western Pacific."
He exhaled, relieved. "Okay. Good. Because for a second I was like, what if that's the Atlantic and I've just been confidently wrong my entire life."
Agnes drifted closer, teasing warmth in her voice. "I would've corrected you gently."
"Liar."
She grinned. "I would've corrected you eventually."
Karl snorted and nudged the controls again as the ravine narrowed. "So… how close are we?"
"To the trench?" she asked.
"Yeah."
Agnes's expression shifted—not alarmed, just thoughtful. Data shimmered faintly around her as she pulled from memory. "Not directly above it. We're still a significant distance east. But… conceptually?" She gestured at the darkness outside. "This is the same world. Same abyss. Same rules."
Karl stared out the viewport. The light vanished after a few meters, swallowed by black so complete it felt unreal. "That thing's… what, eleven kilometers deep?"
"Approximately 10,984 meters at Challenger Deep," Agnes replied automatically. Then she softened. "That's almost seven miles straight down."
He whistled under his breath. "That's insane."
"It is," she agreed. "The pressure down there is over a thousand atmospheres. Enough to crush most things into… paste."
Karl raised a brow. "Most things?"
She glanced at him sideways. "You're already thinking about whether you could survive it."
"Maybe," he admitted. "With enough nanites."
Agnes didn't laugh this time. She studied him for a long second. "Karl."
"…Yeah?"
"Do not get ideas."
He smiled innocently. "I'm just appreciating the engineering challenge."
"You say that like you wouldn't actually try it."
He didn't answer. That was answer enough.
Agnes sighed, drifting closer until she was nearly shoulder-to-shoulder with him. "The Mariana Trench isn't just deep. It's isolated. Cold. Silent. No light. Barely any life—at least, none that we understand well."
"Sounds familiar," Karl said quietly.
She looked at him then, really looked. "Yeah. It does."
They continued through the ravine, stone walls sliding past in tense proximity. In some places, Karl had to angle the sub just right, nanites subtly reshaping protrusions along the hull to avoid catching. The ocean pressed in from all sides, patient and immense.
"You know," Agnes said after a while, voice softer, "humans sent probes down there long before the world ended. Fragile little things. Cameras. Sensors."
"And?"
"And the trench destroyed most of them," she said. "Crushed them. Lost them. Took them like they were nothing."
Karl's grip tightened slightly. "But they kept trying."
"Yes," Agnes said, smiling faintly. "They kept trying."
The ravine dipped sharply, forcing Karl to compensate. The sub creaked—just a little—but held. Nanites flared and settled.
"So," he said, "if we're already dealing with this kind of pressure now… how bad would it be down there, really?"
Agnes folded her arms, considering. "With the sub as it is now? Lethal. With you reinforcing it continuously?" She tilted her head. "Still extremely dangerous. Sustained reinforcement would drain you fast. And if anything went wrong…" She trailed off.
Karl nodded. "Yeah. Bad idea."
She relaxed, relieved. "Good."
A beat passed.
"…But theoretically—"
"Karl."
He laughed, holding up a hand. "Okay, okay. I'll behave."
They reached the narrowest point of the ravine then, stone closing in so tightly that the lights reflected off both walls at once, creating the illusion that the sub was trapped inside a tunnel of bone. Karl slowed to a crawl, breath steady, movements precise.
Agnes leaned closer, voice barely above a whisper. "You know what people called the trench sometimes?"
"What?"
"'The ultimate abyss,'" she said. "A place the sun has never touched. Where the Earth folds in on itself."
Karl guided them through the gap, hull clearing by centimeters. "Sounds dramatic."
"It is," she replied. "But also kind of beautiful."
The sub emerged from the tightest section, the ravine widening just enough to let Karl breathe again. He eased the thrusters, posture relaxing.
"…You think we'll ever see it?" he asked quietly.
Agnes hovered beside him, light warm and steady. "Maybe. If the world ever gives us a moment to just… look."
He smiled faintly. "I'd like that."
"So would I," she said.
They moved on, deeper into the Pacific's shadowed veins, the thought of the Mariana Trench lingering between them—not as a destination, but as a reminder.
There were still places in the world vast enough to humble even monsters.
And for now, that was enough.