The First Vein was unlike anything Elias had seen in the Tower.

  They emerged from the narrow transition passage onto a ledge of hardened tissue, and Elias felt his breath catch in his throat. Before them stretched a tunnel of impossible scale—a massive arterial channel that dwarfed every passage they'd traveled through, every chamber they'd sheltered in, every biome they'd crossed. The tunnel stretched into darkness in both directions, its far end invisible, its scope almost incomprehensible.

  And through its center flowed a river of blood.

  Not the trickles and pools they'd encountered on lower floors. Not the harvested blood that filled his reserves or the transfusion fluid that sustained Lira. This was a torrent—a rushing, churning flow of deep crimson that filled the bottom third of the tunnel, moving with the relentless power of a flooded river. The sound of it filled the space, a constant roar that vibrated through the walls and up through Elias's feet.

  "God," Mira breathed beside him. "It's... it's a river. An actual river of blood."

  "The Tower's primary circulatory channel," Elias said, his medical mind struggling to process the scale. "Old Tom's notes mentioned it, but I didn't... I couldn't have imagined this."

  The blood flow was thick and dark, almost black in places where it ran deepest. Occasionally, paler streaks swirled through the current—arterial blood mixing with venous, oxygenated with deoxygenated, creating patterns that were almost hypnotic to watch. The surface of the flow wasn't smooth; it churned and bubbled, creating waves that lapped against the tunnel walls with wet, organic sounds.

  And the smell. Copper and iron and something else, something wrong, a toxic undercurrent that made Elias's eyes water and his throat burn. This wasn't blood as he understood it. This was something the Tower had made, something designed for purposes he couldn't fathom.

  "Don't touch it," he said, though the warning was probably unnecessary. "That's not normal blood. The concentration of... something... is off. It would probably burn through skin on contact."

  "Wasn't planning on swimming," Mira replied dryly. "How do we get across? Or through? Or whatever we need to do?"

  Elias studied the tunnel, looking for options. The ledge they stood on was perhaps ten feet wide, carved or grown from the tunnel wall about twenty feet above the blood flow. It continued along the wall in both directions, narrowing in places but never quite disappearing.

  "We follow the ledge," he said. "According to Tom's notes, the First Vein runs for about two floors before the passage widens and the blood flow disperses into smaller channels. If we can make it that far, we should reach the transition to Floor 17."

  "Two floors of walking along a narrow ledge above a river of toxic blood." Mira's voice was flat. "In the dark. With whatever lives in here."

  "Yes."

  "Wonderful."

  Lira drifted forward, her ghostly form hovering over the edge of the ledge, peering down at the churning flow below. Her flickering had stabilized somewhat since they'd left the Rest Station, but she still wasn't right, her edges too soft, her glow too dim.

  "It's warm, Papa," she said quietly. "The blood. I can feel its warmth from here. It's like... like the whole tunnel is alive."

  "It is alive," Elias replied. "The Tower is alive. This is just more obvious about it."

  They began their journey along the ledge, moving single file with Elias in the lead, Mira bringing up the rear, and Lira drifting between them. The footing was treacherous—the organic surface was slick with condensation from the blood flow below, and the ledge itself was uneven, sometimes wide enough to walk comfortably and sometimes narrowing to barely a foot across.

  The walls of the tunnel were the most striking feature. Unlike the relatively uniform tissue of the lower floors, the First Vein's walls were covered in a network of smaller vessels—veins and arteries that branched and merged in complex patterns, pulsing with their own internal flows. The effect was like walking through the inside of a massive organism, surrounded by its circulatory system, hearing its heartbeat in the constant rush of blood below.

  The ceiling soared above them, so high that the bioluminescent organs that dotted it were reduced to dim points of light, like red stars in a fleshy sky. Elias estimated the height at roughly one hundred and fifty feet—high enough that sound echoed strangely, high enough that anything living up there would be invisible in the shadows.

  The red glow that permeated the space came from the blood itself. The flow emitted a faint luminescence, just enough to see by, just enough to turn everything the color of old wounds. It was disorienting, that constant red light—it made it hard to judge distance, hard to distinguish features, hard to tell where the walls ended and the shadows began.

  "This place is a nightmare," Mira muttered from behind him.

  "It's a transport system," Elias replied, trying to impose clinical understanding on the horror around them. "The Tower needs to move blood through its body, just like any organism. This is how it does it."

  "That doesn't make it less of a nightmare."

  They traveled in silence for perhaps an hour, the ledge taking them deeper into the First Vein, the blood flow roaring ceaselessly below. Elias kept Blood-Sight active, scanning for threats, watching for any sign of the creatures Old Tom had warned about.

  He found them soon enough.

  The first one was attached to the wall about fifty feet ahead, its body pressed flat against the tissue, almost invisible in the dim red light. If not for Blood-Sight, Elias would have walked right past it—would have walked right into it.

  He held up a hand, signaling a halt.

  "What is it?" Mira whispered.

  "Vein Leech. On the wall ahead. Don't move."

  Through his enhanced vision, Elias could see the creature clearly. It was roughly three feet long, its body segmented and flexible, covered in a slick mucous membrane that glistened wetly in the blood-glow. Its head—if it could be called a head—was a circular mouth lined with concentric rings of teeth, like a lamprey's, designed for latching onto flesh and not letting go.

  The creature wasn't moving. Its body was completely still, its mouth pressed against the wall, apparently dormant.

  "Is it sleeping?" Mira asked.

  "I think so. Tom's notes mentioned that they're sensitive to vibration—they hunt by feeling movement through the walls and the blood flow. If we're quiet enough, we might be able to sneak past."

  "Might?"

  "Tom's notes weren't entirely clear on their sensory range."

  They crept forward, each step careful and deliberate, avoiding any movement that might send vibrations through the organic surface. The Vein Leech remained motionless as they approached, its body relaxed in what Elias hoped was deep sleep.

  As they drew level with the creature, Elias got a closer look at its anatomy. The segmented body was filled with blood—he could see it through the translucent skin, a dark mass that filled most of its interior. A parasite, then, that fed on the Tower's circulatory system, latching onto the walls and draining blood directly.

  You could be reading stolen content. Head to the original site for the genuine story.

  Or latching onto Climbers, if given the opportunity.

  They passed within arm's reach of the sleeping Leech, close enough that Elias could smell its rancid odor over the copper-and-bile scent of the blood flow. The creature didn't stir.

  Ten feet past it, Elias allowed himself to breathe again.

  "One down," Mira whispered. "How many more?"

  "I don't know. But if there's one, there are probably—"

  His Blood-Sight flickered, then expanded, revealing more signatures ahead. Many more.

  "—dozens."

  The tunnel ahead was infested. Vein Leeches clung to every surface—the walls, the ceiling, even the underside of the ledge they were walking on. There had to be at least forty of them visible within his range, and probably more beyond it.

  "We can't sneak past that many," Mira said, her voice tight.

  "No. We can't." Elias studied the pattern of the Leeches, looking for any opening, any path through. "Not while they're awake."

  "They're sleeping now."

  "Some of them are. But look—" He pointed toward a section of wall where several Leeches were moving, their bodies rippling as they repositioned themselves. "They take shifts. Some sleep while others watch. If we try to pass now, the active ones will sense us."

  "So what do we do? Wait for them all to sleep?"

  "That might be exactly what we do." Elias pulled out Old Tom's notes, scanning for any information about Vein Leech behavior. "Here. Tom mentions that the Leeches have a circadian rhythm tied to the Tower's internal cycles. During what he calls 'night'—a period when the blood flow slows slightly and the bioluminescence dims—they all go dormant. It's the only time they're all asleep at once."

  "How long until 'night'?"

  Elias checked the timing against his internal count of hours since entering the Tower. The rhythm wasn't perfect—the Tower's cycles didn't match anything external—but there was a pattern.

  "About three hours. If Tom's observations are still accurate."

  "Three hours of waiting. In this place."

  "Better than dying."

  They found a wider section of ledge and settled in to wait, pressing themselves against the wall, making themselves as small and still as possible. The Vein Leeches continued their movements in the distance, their bodies rippling with disturbing fluidity, their lamprey mouths occasionally opening and closing as if tasting the air.

  The three hours passed slowly.

  Elias used the time to check on Lira, whose flickering had grown worse again during their journey. Her form was unstable, edges blurring and reforming, her usual pale blue glow now shot through with darker patches that came and went without pattern.

  "How are you feeling, sweetheart?"

  "Strange." Her voice was distorted, as if coming through a bad connection. "Like I'm... like I'm not all here. Parts of me keep drifting away and I have to pull them back."

  Elias's heart clenched. "You're doing great. Just hold on a little longer."

  "I'm trying, Papa." She drifted closer, her translucent form hovering near his face. "Papa? Who's that woman with us?"

  The question hit Elias like a physical blow.

  "What?"

  "The woman." Lira gestured vaguely toward where Mira sat. "I know she's important, but I can't... I can't remember her name. I know I knew it before. But now it's gone."

  Elias looked at Mira, whose expression had gone carefully blank—the face of someone who understood exactly what was happening and was trying not to react.

  "Her name is Mira," Elias said gently. "She's our friend. She's been traveling with us since Floor 7."

  "Mira." Lira repeated the name slowly, as if tasting it. "Mira. That's... that's right. I remember now. Mira." Her form flickered violently, and when it stabilized, there were tears in her eyes—tears that couldn't fall, that simply hung suspended in her ghostly face. "Papa, I forgot her name. I knew it, and then I didn't, and I couldn't find it anywhere in my head. What's happening to me?"

  Elias reached for her instinctively, his hands passing through her form as they always did, unable to offer the comfort of touch.

  "You're going to be okay," he said, the words feeling hollow even as he spoke them. "The Soul Integrity decline is causing some... some memory issues. But once we reach the Origin Blood, once I can stabilize you properly, it'll all come back. I promise."

  "But what if I forget more? What if I forget you?"

  The fear in her voice was devastating. Elias had faced monsters, fought for his life, made impossible choices in the darkness of the Tower. But nothing had prepared him for this—for the terror of watching his daughter's mind slowly erode, for the possibility that she might forget him before he could save her.

  "You won't forget me," he said firmly. "I won't let you. No matter what happens, you'll always remember me. I'll make sure of it."

  Lira's flickering stabilized slightly, the desperate reassurance seeming to anchor her somehow.

  "Okay, Papa. I trust you."

  Mira caught his eye, her expression grim. She didn't say anything—there was nothing to say—but her understanding was clear. The clock wasn't just ticking. It was accelerating.

  The three hours passed, and slowly, the First Vein began to change.

  The blood flow below didn't stop, but it slowed—the roaring current diminishing to a gentler rush, the churning surface smoothing slightly. The bioluminescent organs in the ceiling dimmed, their red glow fading to something barely perceptible, plunging the tunnel into deeper darkness.

  And the Vein Leeches went still.

  Through Blood-Sight, Elias watched as every creature in range stopped moving, their bodies relaxing against the walls, their circular mouths closing. The pattern was unmistakable—a synchronized dormancy, the entire population entering sleep at once.

  "Now," Elias whispered. "Move slowly. No sudden vibrations."

  They crept forward through the darkness, the dim red glow barely enough to see by, Blood-Sight providing the real navigation. The Vein Leeches were everywhere—attached to walls mere feet away, clinging to the ceiling above, pressed against the underside of the ledge they walked on. Each step was an exercise in controlled terror, every movement calculated to avoid the slightest tremor that might wake the sleeping parasites.

  The ledge narrowed in places, forcing them to press against the wall and shuffle sideways. In one section, a Vein Leech was attached directly to the path, its body blocking half the ledge, and they had to step over it—Elias holding his breath as his foot came within inches of the creature's slick skin.

  It didn't wake.

  They traveled for what felt like hours, though it was probably less than one. The tension was exhausting, the constant vigilance draining in a way that combat never was. Every sound, every shift in the air, every tiny vibration sent spikes of adrenaline through Elias's system.

  But they made it.

  The tunnel began to widen ahead, the walls spreading apart, the blood flow dispersing into smaller channels that branched off in different directions. The concentration of Vein Leeches thinned as the ecosystem changed, the parasites preferring the main channel to the tributaries.

  And then Elias saw the body.

  It was wedged in a crevice where the main tunnel met one of the smaller channels—a human form, motionless and partially submerged in the shallow blood that pooled at the junction. Male, from what Elias could see. Wearing the remains of Climber gear.

  Dead.

  "Wait here," he murmured to Mira, and crept forward to investigate.

  The Climber had been dead for a while—days at least, maybe longer. The blood flow had preserved the body somewhat, but the damage was evident. Deep wounds across the torso, probably from Vein Leech attacks. He'd made it this far and then collapsed, either from blood loss or exhaustion.

  Another Climber who hadn't made it. Another life claimed by the Tower's hunger.

  Elias searched the body quickly, finding nothing useful in the waterlogged pack. But the man's blood...

  He hesitated. This wasn't harvesting from a creature, or even from an enemy. This was a fellow Climber, someone who had fought the same battles Elias was fighting, who had died trying to do the impossible.

  But Lira's face when she'd forgotten Mira's name. The flickering. The fear in her voice.

  Elias activated his harvesting ability.

  Harvested Blood: +1.2 L

  Blood Reserves: 4.3 L

  "I'm sorry," he murmured to the corpse. "I hope you understand."

  He returned to Mira and Lira, not mentioning what he'd done. Mira probably knew anyway—she'd seen enough of the Tower to understand the necessities—but some things didn't need to be spoken aloud.

  They continued forward, leaving the First Vein behind, entering the transition zone to Floor 17. The passage here was more familiar—organic but smaller, closer to the tunnels they'd traveled through on lower floors. The constant red glow faded, replaced by the softer blue of standard bioluminescence.

  And ahead, visible in the distance, was the gate to Floor 20.

  It was larger than the other floor transitions Elias had seen—an archway of hardened tissue, perhaps thirty feet tall, marking the entrance to a major Rest Station. According to Old Tom's notes, Floor 20 was a hub of sorts, a place where multiple routes converged, where Climbers could rest and resupply before the more dangerous floors ahead.

  Safety. Resources. A chance to help Lira.

  But something was wrong.

  A shadow moved behind the gate.

  Not a person, the shape was wrong, too large, too irregular. It shifted in the darkness beyond the archway, a massive form that seemed to fill the passage, blocking the way forward.

  Elias activated Blood-Sight, extending his range as far as it would go.

  The creature's blood signature was enormous—a complex network of vessels that suggested a body at least twenty feet tall, with multiple limbs and a central mass that pulsed with powerful circulation. It wasn't moving toward them, but it wasn't moving away either. It was waiting.

  Guarding.

  "What is that?" Mira whispered, her hand going to her knife.

  Elias remembered Old Tom's notes, the warnings about the deeper floors, the creatures that protected the Tower's vital points.

  "That's the Dermis Warden," he said quietly.

  "How do we kill it?"

  Elias stared at the massive shadow, at the blood signature that dwarfed anything he'd encountered, at the guardian that stood between them and any hope of saving his daughter.

  "I don't know yet."