The deeper they went, the less the refinery felt like a place people worked and the more it felt like a place people offered things.
The corridors shed their "industrial" skin. The scuffed metal, the practical grates, the honest grime—gone. In its place: cleaner panels, tighter seams, lights that didn't flicker like faulty wiring but held steady like an interrogation. The air turned dry and sharp, filtered until it tasted like nothing, which somehow made it worse. Like Shinra had scrubbed the oxygen so they wouldn't have to breathe the same atmosphere as their guilt.
Zack could still smell the town burning anyway.
It wasn't strong down here—just a ghost-thread of smoke that snuck in on his clothes and caught in the back of his throat when he swallowed. Like Nibelheim was clinging to him on purpose. Like the place was trying to leave fingerprints on the moment so nobody could pretend it didn't happen later.
Ahead, Sephiroth didn't slow.
He moved with that same calm he'd had in the archive—calm as a decision, calm as a blade. The green light found him in waves through vents and seams, and each time it did, it made him look less like someone you could grab by the shoulder and more like something you met in old stories right before everything went bad.
Zack kept trying to find a line that would hook him back.
Not an order. Orders were for troopers and paperwork and people who still believed Shinra's voice deserved obedience. Zack needed something older than that. Something human. Something stupid enough to be true.
"Seph," he called, not loud, not soft—just there. A name thrown like a rope.
Sephiroth didn't look back.
The hum was louder down here. Not louder in your ears—louder in your bones. It filled the spaces between the metal plates and made the whole building feel like a giant instrument being played by a hand you couldn't see. Every few seconds the frequency changed, subtle as a breath shifting in sleep, and Zack caught himself adjusting his own breathing in response like an idiot.
Like the refinery was teaching him a rhythm.
They passed a sealed door marked with warnings so aggressively bold they almost sounded like pleading. The Captain wasn't with them anymore—somewhere behind, swallowed by panic or orders or whatever Shinra used to keep its people obedient. The troopers had thinned out too, falling back as if they'd hit an invisible boundary and suddenly remembered they had families.
Zack didn't blame them.
He felt it too: that sensation of crossing from "mission site" into threshold. The kind of line that doesn't show up on maps but still changes the air.
Sephiroth keyed in a final sequence without hesitation. The lock disengaged with a smooth click that sounded indecently polite.
Then the door opened.
Heat hit Zack like a shove.
Not the cozy heat of a fire in a hearth. Not even the brutal heat of a burning house. This was heat with infrastructure. Heat produced on purpose. Heat contained by engineering that didn't care what it scorched along the way.
Beyond the door, the core chamber yawned open into something that didn't feel like a room at all.
It was a cathedral. A vast industrial nave carved out of the mountain, scaffolding rising like ribs, cranes and gantries hanging like crooked chandeliers. Catwalks webbed the air in overlapping layers, thin lines of metal stretched over emptiness, leading to platforms that looked too small to be safe and too important to be optional.
Below them—far below, so far Zack's depth perception flinched—mako moved in open channels like an exposed artery.
Not contained behind glass. Not politely hidden. Open.
It wasn't just glowing. It was roaring, luminous and violent, slamming itself against containment walls as if the planet was trying to climb out. The light was so bright it turned the underside of every catwalk into a hard-edged silhouette, stripping detail away until everything became shadow-shapes and motion.
Heat distortion shimmered up from it in thick waves, bending the geometry of the chamber like a mirage. Straight railings wavered. Hard corners softened. For half a second at a time, it looked like the whole refinery was melting—like the mountain itself was tired of holding Shinra's sins and was starting to liquefy out of spite.
Zack stepped onto the first catwalk and immediately felt the slickness under his boots. Condensation. The air was so hot and so saturated with energy that the metal sweated, beadlets gathering along the grating and the railings. His palm slid when he grabbed the side.
He tightened his grip anyway.
The sound down here wasn't a hum anymore. It was a throat. It was the Lifestream forced through turbines and pipes and containment channels, and it didn't sing so much as it endured. A deep, endless tone threaded with mechanical grind, like a choir locked inside an engine.
Zack swallowed, and the sound swallowed with him.
Sephiroth walked onto the catwalk like the heat didn't exist.
Like the roar below wasn't a warning.
He didn't glance down. He didn't hesitate at the narrowness. He moved with the simple certainty of someone who had already decided how this ends, and was just letting the universe catch up.
Zack followed, because of course he did.
Because there was still a piece of him that believed you could grab someone by the collar right before they jumped and drag them back, even if it broke your hands.
Because there was still a piece of him that remembered Sephiroth laughing—actually laughing, once, months ago, when Zack had tried to balance a tray of cafeteria slop on the edge of his sword like it was a party trick. It had been rare, quick, surprised out of him like a crack in stone.
Zack clung to that memory like it was proof.
They reached a wider platform where the catwalks converged, a junction built around a heavy access gate set into the floor. Thick locking mechanisms. Warning lights. Control panels arranged with ceremonial precision, as if the core itself was something you had to ask permission to approach.
The gate led downward—into the brightest, hottest heart of the whole structure.
Sephiroth angled toward it without slowing.
Zack stepped in front of him.
Not a dramatic leap. Not a soldier's block. Just a human act: placing your body where you don't want someone else to go.
The heat made his skin itch. The mako light painted his arms green-white. His shadow stretched behind him in long, sharp pieces. He could feel the vibration of the machinery through the soles of his boots, through bone, through teeth, like the refinery was trying to shake him apart into smaller, more cooperative parts.
Zack lifted his chin anyway.
"Whatever is whispering to you," he said, and his voice came out rougher than he meant, scraped raw by smoke and panic and the sheer pressure of this place. He forced the words into shape. Forced them to stay steady. "Whatever you think you found—"
He watched Sephiroth's face as he spoke, hunting for any sign of the man he knew. Any fracture. Any hesitation. Any flicker of please help me.
Sephiroth's expression didn't harden.
That was the problem.
He looked almost… gentle.
Not in the way you looked at someone you loved.
In the way you looked at someone you were grateful to, right before you left them behind.
"It's using you," Zack finished, quieter now, because yelling felt stupid against a river of the planet's blood. "It's wearing you like a uniform."
For a heartbeat, the only thing between them was heat and green light and the roar below. Zack's breath fogged faintly in the strange air—cool condensation in a furnace. He could see his own pulse in the way his hand trembled against the strap of the Buster Sword.
Sephiroth's eyes stayed on him.
And for the first time since the archive, Zack felt like Sephiroth was actually seeing him—really seeing him—like he was looking at the last thread tying him to the person he'd been.
Sephiroth's mouth curved, small and soft, not mocking. Almost affectionate.
"No," he said.
The word landed with terrifying calm.
"It's freeing me."
And the chamber seemed to listen when he said it—like the mako below surged in approval, like the refinery itself leaned closer, hungry to hear what he'd choose next.
Zack didn't move.
He couldn't.
Because some part of him understood, all at once, with cold clarity:
This wasn't a negotiation anymore.
This was the ledge. This was the point where you either pull someone back, or you watch them step into a new name.
And Sephiroth—Sephiroth looked past Zack at the core access gate like it was an altar waiting for him to kneel.