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Diluc hadn’t always been like this.
When he went out at night, slashing through mobs with ease, people would thank him. They revered him, whispered tales of a darkly-dressed hero spreading like wildfire. He heard what his patrons said, lips loose after a night of drinking, singing his praises in relief that someone was watching. That someone cared.
He knew Mondstadt’s people had learned not to fear the darkness of the night, comforted by his presence. It was better to take matters into his own hands when the Knights did fuck all. It was moments like these when he was wiping his blade clean of slime secretion that his guard slipped.
The figure attacked from behind— a coward’s ways, he sneered. They moved with an inhuman speed, able to twist the blade out of Diluc’s hand and knock him onto his back.
Blood rushed to his head as he tried to identify the man atop him. A black cloak with its hood drawn up obscured most of his features, even as Diluc rabidly bucked off of damp grass, trying to dislodge him.
The man seemed to grow tired of his antics, grabbing him by the collar and slamming him back into the ground. He groaned as his head bounced hard enough to concuss.
“Get off me,” Diluc grunted, half-heartedly reaching for the knotted strings holding the man's cloak together.
A pale hand snatched his hands mid-air, before he could make contact, and the man shifted his weight to pin his wrists down to the grass above his head.
Diluc flexed his wrists, testing his strength. He could hardly budge. “What are you?”
With his training regime, it shouldn’t be physically possible for a man of this size to pin him down.
The man leaned closer, unspeaking. A ray of moonlight hit the lower half of his jaw, illuminating blood red lips and fangs as they crept closer and closer to Diluc’s neck.
You’ve got to be kidding me, Diluc thought in disbelief as those teeth sunk into him. The pain was little more than a prick, but the throbbing in his head worsened, black spots dotting his vision as the apparent vampire drank his fill.
He sunk into darkness to the feeling of a sandpaper tongue dragging across the wound.
When Diluc awoke to the sun beaming over him, the headache was gone. So were the various cuts and bruises he’d worked up after a night of patrol.
He raised a hand to his lips, running a finger over the bottom of his teeth. They didn’t feel any different. He prodded at his gums, pausing over his canines. The flesh there felt harder, as though there was something underneath.
He quickly pulled his hand out, wiping his fingers on his coat. This was ridiculous, the notion that Diluc was one of them now, the very creatures he spent his life fighting.
He would be fine. And in the beginning, he was.
The hunger came in flashes. It started with the weakness, his mind going foggy and the new speed he’d come to appreciate fading into sludgy movements. Then, his stomach began to ache. Diluc had been fortunate enough in his life as a human to never go hungry. It was a new discomfort, one that he struggled with, when the solution came from taking a life. The final straw had been when his fangs ripped through his gums, sliding over his canines with a sharper edge, meant to tear through layers of skin and muscle.
The first time it happened, he’d been blinded by the pain, barely able to stumble into the forest as his gums bruised with their new additions.
Luckily, the woods of Mondstadt were more animal than man. An ox was better than a human, he reasoned, once the bloodthirst had been sated.
It kept happening, becoming harder to control as his senses sharpened and all he could smell was warm, pumping blood around him. When he donned his armour and escaped to the streets, being able to smell the fear, then the upmost gratitude of the sheep he’d lead in a different life, it was harder to remember he was to be their saviour, not monster.
It had been the blind trust that made it easy for him to creep up behind them, clamp a hand over their mouth, and take what he needed.
“I’ve got a new assignment,” Kaeya said one night, eyes half-glazed over an empty pitcher.
Diluc kept his face calm, his grip tight as he took a sip of his wine, ignoring the ache in his teeth and the stench of sweat in the tavern.
“People keeping showing up with bite marks on their necks, shoulders, thighs—“ he gestured for Diluc to top him up, which he ignored “—and not a memory of how they got them.”
“That sounds like a fetish,” Diluc said bluntly. “Are you sure you’re not being played?”
Kaeya snorted, shaking his head. “It seemed like a joke at first, the missing memories were convenient. But the reports haven’t stopped, and they’re coming from every corner of Mondstadt.”
He leaned closer, enough so that Diluc could smell his alcohol-tanged breath. “Jean doesn’t want this getting out,” he murmured, low enough that even inches away, Diluc’s ears strained to listen. “She thinks it’s a mythical problem. The storybook kind that sleep upside down.”
Diluc raised an eyebrow. “Vampires in Mondstadt. I suppose you’re going to be the one to slay them?”
“Don’t be ridiculous,” Kaeya scoffed, settling back into his seat. “I’m on research for now; after all, I’ll need to be able to find their secrets to kill them.”
Diluc hummed, drumming his fingers against the table. “You could’ve come to me earlier. I’ve heard a fair bit about their kind,” he said, knowing the words would get under his skin. Kaeya always hated being at a disadvantage, moreso when it was Diluc was holding information from him.
Like clockwork, Kaeya's face scrunched up.
“Right,” a drunken giggle bubbled out his lips. “Of course you know all about vampires. How silly of me to assume wouldn't help me when you start growling every time I visit."
Diluc’s nails dug into the meat of his palm as he pushed down the flare of anger that came with old memories. “You and I both want what’s best for the people of Mondstat, regardless of how we see that through.”
“Believe me, I know.” Kaeya rolled his eyes. “You were always one for theatrics. And I suppose you see yourself too good to come running back to the actual knights.”
“Keep your voice down,” Diluc said coldly, eyes darting around the tavern for listeners. “Mock me to your heart’s content; you can’t deny that my methods are effective.”
“That’s the only reason I haven’t ratted you out,” Kaeya hummed. “The bounty for information on the Darknight is quite high. The moment you step out of line, I’ll be an odd thousand Mora richer.”
Meeting blue eyes that were dead serious, Diluc didn’t doubt him.
“I’ll leave you to your night,” Kaeya finally said, pushing off the bar stool. “I’ll be by the Winery this week. I need to check your father’s books for information on vampires. You understand, don’t you?“
There was no room for question in his words.
“Yes, captain.” Diluc murmured. He turned away, watching through half an eye as Kaeya nodded, satisfied, and turned to leave himself.
The door of the tavern slammed shut, and Diluc released a breath. He had some nerve, walking in here as though things were fine between them. As if Kaeya had done nearly enough to earn Diluc’s forgiveness and an invitation to his home.
Kaeya made haste on his words, appearing on his doorstep surprisingly early for the late night he’d had. There were dark circles under his eyes and a leather satchel slung over his shoulder.
Diluc opened the door, nodding in greeting as Kaeya stepped inside, his hesitation invisible to anyone who wasn’t as observant as Diluc.
“Do you have the books?” He asked without any preamble.
“I’m good, thanks for asking.” Diluc headed for the kitchen, pouring himself a cup of dandelion wine, knowing he’d need it to get through this conversation. “Drink?” he offered, holding a second glass out to Kaeya.
“I didn’t come here for alcohol,” Kaeya sneered. “I need information, to keep the city you swore to protect safe.”
“That’s a shame, it’d do wonders for the stick you’ve shoved up your ass.”
“Funny,” Kaeya deadpanned. “I’ll be in the study.”
Diluc hummed in acknowledgement. He’d already checked Crepus’ records and pulled out the books with mentions of vampires.
He wondered if he wanted to get caught. Diluc knew his former self would be disappointed in his lack of self control, but this was his nature now. He was a superior species, the top of the food chain, where a human was no different than a rabid animal.
Finishing off his cup, he stood, heading to the brewery. Kaeya might spend all day riffling through books; Diluc had a business to run.
Through the morning, he worked up quite the appetite, enough so that he was sneaking away in the afternoon to hunt. It was exhilarating, sinking his teeth into screaming flesh, knowing Kaeya was half a dozen clicks away, worrying his pretty head on finding the monster living under his nose.
By the time he finished the day’s work, mostly inventory, the sun was already setting. The workers were long gone, leaving the Winery quiet save for his own footsteps.
He knocked once on the study door, pushing it open to reveal books strewn all over the floor, Kaeya in the centre, mumbling nonsense as he scribbled into his journal.
“Are you staying for dinner?”
His head snapped up, as though he’d forgotten this was Diluc’s house. “Dinner— what time is it?”
Diluc tilted his head to the window, Kaeya’s eyes following the movement to the orange skies.
“Come take a break, Adelaide prepared enough fish for the both of us.” Diluc didn’t wait for an answer, leaving towards the dining hall. Usually, he ate alone at the long table. It would be nice to have company, even as irritating as Kaeya was.
A few moments later, he heard Kaeya’s sigh and footsteps began following him. The trays were already waiting for them on the table, as Diluc had instructed once he realized Kaeya had no plans of getting food himself.
He took his seat at the head of the table, tucking a napkin into his collar as Kaeya entered the room.
“You’ve redecorated,” he noted, voice devoid of any emotion.
Diluc shrugged, cutting his fish into thinner slices. “Crepus was good at many things. Interior design was never one of them.”
His eyes trailed over the changes he’d made. The most noticeable one, a portrait of three hanging on the wall. “You’d know, if you ever bothered showing up.”
“You made it very clear I wasn’t welcome here,” Kaeya said coldly, stabbing at his plate.
He ignored the anger in Kaeya’s voice, taking his time to chew before replying. “Maybe I’ve changed my mind.”
“How generous of you,” Kaeya sneered. “I’m not looking for your forgiveness. I’m not looking to come ‘home,’ this trip has been purely business.”
“I suppose I have to take your word as Captain,” Diluc sighed. “I do wish things had ended differently between us, though.”
Kaeya seemed lost for words, breaking away from Diluc’s gaze and purposely taking another bite. He supposed this was a lot to spring on him over dinner.
“I‘ll help you with your research tonight,” he said, hoping it came across as a show of good faith.
Kaeya didn’t seem enthused at the prospect of his help, but he didn’t protest.
It was a far cry from where they’d been months ago.
Baby steps, Diluc reminded himself. It wouldn’t do him well to scare him off so soon.
“This is what I’ve gathered so far,” Kaeya said, pushing his journal into Diluc’s hands. “The books I read through weren’t very specific. Some contradicted others. Some were so outlandish they had to be fiction, but it’s all written there.”
Diluc hummed, skimming through the pages. He’d done a thorough job, listing everything from potentially enhanced strengths, to weakness in the sun, to transforming into actual bats.
“They don’t even have a connection to bats. The only similarity is having fangs,” Kaeya ranted. “So do hippopotamuses, and no one says they’re all vampires.”
“Not the only similarity," Diluc absentmindedly corrected.
"What?"
"Bats and vampires are also both nocturnal."
He looked up when Kaeya didn’t respond. His eyes were trained on Diluc, eyebrows furrowed together. “I never wrote that they’re nocturnal.”
Shit.
He shrugged nonchalantly. “Most of the incidents you recorded have been at night. It only makes sense.”
“Right,” Kaeya said, slowly. “Write that down.”
Diluc obliged, neatly listing the observation under Kaeya’s increasingly messy handwriting.
“So we have a rough idea of their timing, but not how they pick their victims, or how to find them.”
“You could try knocking on every door with a clove of garlic and a mirror,” Diluc drawled, twirling the pen between his fingers.
Kaeya stopped from where he was pacing a hole into the small patches of carpet not covered by books. “That’s not a bad idea.”
“You can’t be serious,” Diluc said, amusement colouring his voice and a singular brow raised in disbelief.
“People are dying,” Kaeya hissed. “We have to do something— and if relying on fairytale myths is what works, then we have to give it a shot.”
“It won’t work,” Diluc said.
“You can’t know that, not until we try,” Kaeya groaned.
“I know it won’t work, because I’ve met a vampire.”
Kaeya’s head snapped towards him, eyes blowing wide. “Bullshit. You didn’t think of mentioning that earlier?”
He was playing a dangerous game. Kaeya had a way of disarming him; it would be all too easy to let something slip. He tilted his head to the side, lightly tugging the collar of his shirt down to reveal two faint scars in the crook of his neck.
“I don’t remember much,” he said, holding still as Kaeya leaned over him, just like the vampire had that night. He flinched, just barely, as Kaeya's cold fingers traced over the marks.
Kaeya’s heart was pumping hard, he could hear it, smell it, practically taste it as shock ran through him. He swatted Kaeya’s hand off him, forcing down the wave of hunger before it overcame him.
“Have you been checked out? I can’t believe you kept this a secret,” Kaeya said, pulling Diluc out of his chair.
“I’m fine,” he protested, easily able to spin them around, pushing into his seat. “It hurt at first, but it healed like all wounds do.”
“Okay,” Kaeya said, sounding more delirious by the second, “You were bit by a vampire. Snuck up on, subdued, and bit, I imagine.”
Diluc nodded in confirmation.
“This is bad,” Kaeya said, flipping to a new page as his voice grew shrill. “That confirms the enhanced strength, at the very least. Do you recall anything from the encounter? Anything it said— or did?”
Diluc contemplated it for a moment, subconsciously tilting his head. “I had been out that night, past the city's Western gates. I remember being tackled, I couldn’t see what was happening, not with all the lights out. I was… scared. I know what I’m capable of against monsters, but this was like nothing I’ve fought before. By the time I woke up, he was long gone.”
“I’m sorry,” Kaeya whispered, startling Diluc out of the memories.
He frowned. “What could you have done?”
“I should’ve been there,” he said, eyes dark and fist clenched around his pen. “I’ll kill whoever’s doing this.”
Diluc swallowed thickly, taken aback by the ferocity of his protectiveness. He didn’t know he still had that. “See that you do.”
He stood, placing his book back on the desk. “It’s been a long day, I’m going to retire for the night. You should get some rest too.”
Diluc felt his eyes on his back as he walked out, quietly shutting the door behind him. He had barely made it to his chambers when his fangs slid out, his stomach snarling for some real food. There was a perfectly edible meal down the hallway.
He waited til Kaeya’s heartbeat slowed to slide out his window.
“Diluc!” someone shouted.
The man in question groaned, covering his ears as a series of knocks pounded on his door.
“I’m going to kick the door open,” the voice— Kaeya, shouted.
“I do hope you’ll be replacing it too, then. Cypress wood isn’t cheap,” he shouted back.
“Oh, thank god, you’re alive,” Kaeya breathed, jiggling the door knob. “There’s been a disaster, open up.”
Diluc rubbed his eyes, mourning a night of real sleep, and rolled off his bed to unlock the door. “What’s the matter?”
Kaeya looked exhausted, his eyes grim and lips pressed into a thin line. “The Winery was attacked; early morning, when the first shift was working.”
“I see,” Diluc said, face devoid of any emotion.
“There’s blood all over the fields. I thought they got you too,” Kaeya whispered. He hesitated, then stepped inside Diluc’s room, pulling him into a hug, even as he instantly stiffened.
“I'm getting tired of this act—” he scoffed, prying Kaeya off him. He wanted Kaeya to work with him, but he wouldn't play house with him. Kaeya blinked in confusion, as if he couldn’t possibly comprehend Diluc’s reaction. “—you’ve never cared about me.”
“That’s not true—“
“You were so happy when I left Mondstadt. You could finally have all the glory for yourself, while I was avenging the man who gave you everything.” He got closer and closer to Kaeya, nearly spitting the words into his face.
“Having a son in the army was Crepus' dream,” Kaeya said, pushing against Diluc, who didn’t budge. “Waging a one-man war against the Fatui won’t bring him back, and he wouldn't want you to waste your life for this.”
“He already had a son in the army,” Diluc snarled, “And it wasn’t you.”
With the midnight meal he had, Diluc hadn’t been expecting his bloodlust to return so soon, but Kaeya’s adrenaline smelled all too sweet. He sniffed the air like a rabid dog, yanking the buttons of his shirt open.
“What are you doing?” Kaeya futilely pushed at his hands, backing up til his back hit the wall.
Diluc smirked, dangerous and full of teeth, closing in on him. “You mean you haven’t figured it out? Perhaps this will help—” finally, he allowed his fangs to slip out, running his tongue over the sharp bottoms.
He felt a sick thrill watching Kaeya’s eyes widen in fear as the realization sunk in.
“How will you serve your country once you're like me?” He crooned, wrapping a hand tight around Kaeya’s neck. “Will your loyalty to Mondstadt last? Will you turn yourself in before you become one of its villains?”
“You're mad,” Kaeya spat, voice hoarse as his fingers pressed deep enough to bruise.
Diluc ignored his squirming, focused on the pulsing vein before him. He tried being gentle, wanting to make this as easy as possible for Kaeya. Some pain was unavoidable, drawing a warbled gasp from Kaeya’s lips as his teeth pierced through skin. His blood sang, heavy in copper and so warm as it filled his mouth. Diluc sucked harder, paying half a mind to Kaeya’s thrashing body, only pulling off when he went limp, blue eyes fluttering shut from blood loss.
“We could do so much together,” Diluc murmured, lapping at the wound. “I wanted you to trust me, for you to choose this life, but you’ve always been too soft.”
“Let me go,” he coughed wetly, trembling in Diluc’s arms.
Diluc shushed him, easily picking him up and walking back to bed. “You need to rest now.”
Kaeya was a smart man, he’d see reason in Diluc’s plans eventually. They were stronger like this, in every which way.
He might’ve been right about the futility of Diluc's one-man war. Now, no longer men, things would be different.