A prompt based short-story using the dual themes of Sci-Fi and Vampires. 

Some things never changed, Seb thought, as he glanced furtively out of the service tunnel's door. Tonight was no different. He breathed in, and his nostrils flooded with the artificial, scented wind that he associated with the Surface side. It was a clear night, and the full moon could just be seen, trying to force its way through the polluted stratosphere. Everything had aged, either for better or worse, except him. Seb had watched the moon morph from silver to a motley grey as humans settled there. That was almost seventy years ago now, and he still didn't look a day over thirty.

It was blindingly bright Surface side, even at night. Seb tried to avoid it where ever possible- he only came up when he was hungry. Here, screens of advertisements assaulted his eyes, and the air was bloated with noise: whirring machinery, far-off music, and laughter. The wireless communications that lingered on the air made Seb's head ache like there was a hive of wasps inside it, which was impossible, seeing as the humans had driven them to extinction.

The outskirts of the space dock were the best place to catch a meal. It was much quieter this far out from the city. Soot from an arriving ship stuck in his throat faster than the molecules in the air could neutralize it. He lay in wait. Finally, the new arrivals drifted out of the dock. Seb could practically hear the blood rising to the surface of their dark skins. His stomach rumbled as he selected his meal. The man had stringy black dreadlocks. He wore a ship mechanic's uniform, and had a duffel bag slung over one shoulder. He was alone. That made him easy picking. Seb stepped out of the service tunnel, tailing his target. He felt disapproving eyes on his back. Some of the new arrivals spat at him after he walked by. It was hard to believe that a couple of centuries ago, their positions would've been reversed. Seb pulled his hood over his head, covering his blonde hair. He wondered idly if they'd still stare if they knew he could rip their spines out from their rib-cages.

His target turned down towards the canal. Seb couldn't believe his luck. The canal was usually deserted on nights like these, when thick mist rose off its surface, rolling in thick waves on top of the water. Obviously, he hadn't heard the rumours. Tough luck for him. Seb liked the canal particularly as there was a service tunnel under the bridge, a couple hundred meters upstream. The man followed the edge of the canal,  heading towards the city center like a moth drawn to the light.

Seb waited until his walking blood-bag has passed the third street lamp, then he sprinted after his target. His senses exploded. He felt the man's shock when he realized he was being chased; a spurring heartbeat; adrenaline in the air. His target's footsteps pounded frantically against the clean, artificially tiled ground. Seb closed the gap between them with ease. It made him feel alive again. He barreled into the man, taking them both over the side of the barrier, and into the canal.

The water was cold and deep, with a strong current flowing through it. Seb pulled his prospective meal to the bottom of the canal, pinning his meal's brown muscled arms to his sides. The man was a fighter, he struggled against his inevitable death. Seb grunted, as the man delivered a particularly powerful kick to his ribs. There was an advantage to not needing to breathe: eventually the man's movements slowed, and Seb relaxed his iron grip. He'd have no chance to savour his prize here though. The Authority would be after him if he didn't make this quick. Seb bit into the crease of the man's arm. Bubbles escaped his meal's mouth. Seb savoured the first draw of the warm blood, relishing it as it slicked the inside of his throat. Then he got to work, leaving the man's blood to mingle in the water like black gold. Carefully, Seb fished the man's microchip out from underneath the dark, ruptured skin. Seb hated the things. They had ruined hunting for him completely. It'd turned hunting, something carnal and invigorating, into what was essentially shoplifting bodies. Never mind the chips' accurate GPS tracking: if they sensed a lack of pulse, they alerted the authorities. Like now. Seb pried the rectangular chip from the man's flesh, and watched the current carry it away. Then he lugged the man into the service tunnels.

The service tunnels linked all parts of the Surface side together, carrying electronic cables along labyrinth-like corridors, like capillaries, lingering just below the Surface. Once deep inside them, Seb stripped the man of his clothes and bundled his limp, still dripping body into a well-used sack. Then he popped out a weakened wall panel, and crept into the consuming darkness. No one would follow him down here. He stood on the edge of a support pylon, a good ten stories above the dim flickering of Subterrania, feeling like a God. Seb lowered himself carefully down a massive support pylon, avoiding the thick wires that branched down it like wending arteries. He could smell blood leaking from the man's arm. Seb's stomach growled. He'd only managed to get a few good gulps when he was wrestling the small electronic chip from his flesh. 

He longed for a war. Something to break the suffocating, monotonous  order of this world that had become so alien to him. What would it take for bombs to fall from the sky like ill-received Christmas gifts? He wanted fleeing citizens, smoke in the air, and blood on the ground. He missed that. To be able hunt, properly, without some Authority demanding a non-existent identity chip, or wondering why he had no heat-signal. Destruction, devastation. Those were what Seb thrived on. He imagined the Surface burning, and felt his fangs erupting from his jaw at the thought. 

Seb reached the ground, and shifted his sack on his shoulder. He dropped the mechanic's clothes at the base of the pylon. Subterrania was a desolate, poorly named place. After all, Seb thought, they it wasn't actually underground: the human race had simply built another Surface on top of the old one. He scuffed his shoe on the crumbling gravel. This was real ground, with dirt, and mud. The Surface didn't have that. It was much quieter down here, in the dark, with crushing blackness spanning in all directions. It made him feel at ease. Ten storeys above him, supported by large rectangular pylons, lay the Surface. Its welded underbelly was a patchwork sky: devoid of stars or clouds. In summer, it creaked under the heat of the sun. 

A row of flickering street lights dimly illuminated his path as he walked down the center of the cracked road. Without proper light, there weren't any proper trees down here. The closest Subterrania could manage was a row of wooden skeletons, hunching pitifully towards the flickering lights. They'd been dead for a long time. Eyes peered down at him anxiously from dirt encrusted windows. He'd lived on the outskirts of the Beta district for nearly a year now, but no one had ever asked him about the sack, or the screams that undoubtedly came from his home shortly after. Seb liked that.

Eventually, the row of dim street lamps came to an end. He watched his shadow become one with the darkness around him. Seb liked the darkness. In it, he could sense the beating of hearts, hear the scuffling of Subs through the streets. He almost felt sorry for them: the humans who couldn't afford chips; the mad ones; the pale ones; the ones forced out of society. In a way, he saw so much of himself in their pale, weedy bodies, and the thought filled him with self-revulsion. We're the ones who fell through the cracks, he thought. Down here, Seb only went after the ones who no one would miss, and the violent criminals, of course. They were fun to play with. But Surface side? Seb grinned, and shook his sack for good measure. On the Surface, anyone was fair game.

Seb liked where he lived. The dilapidated house had a roof that sunk inwards like an upside-down satellite dish. It was nestled in between a Surface support pylon, and a long-abandoned, flooded subway tunnel: two exit points should he need to leave in a hurry. It had all the usual alterations: he'd reinforced the rotting picket fence with barbed wire (stolen from the service tunnels above); covered over the windows with rusted iron; and stoppered up the hole in the roof. It was dark, dank, and paint flaked off the outside of it like rotting skin. It suited him very much. Seb swung the door open, and deposited the sack into the corner of the room. The sack groaned. That didn't normally happen, Seb thought. He was sure that the human had drowned. Seb kicked the sack gingerly, just to be sure. Another groan. Well, that's unfortunate, he thought.

A male voice quavered from within the sack. "Hello? Is anyone there?"

Seb rolled his eyes. He'd forgotten how dense humans were. He dead-bolted the doors, and retired to his reflection room, where ninety-eight empty eye-sockets stared back at him. Seb was quite proud of his catacomb, he got a lukewarm burst of feeling (where his heart used to beat) every time he thought about it. He sighed, lit a small candle, and placed it inside one of the skulls. Relaxing shadows flickered up the ancient wall.

He savoured the moments before his kill. Resting, envisioning, listening to the frantic rhythm of the man's heart. Mostly though, he waited; holding himself back for the moment when the man would fight his way out of the sack. Seb wanted to watch the last gleam of hope drain from the man's eyes when he realized his fate. A triumphant shout sounded from the front room. Seb felt his fangs slide out. The wait was over.