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For the first time in a long time, Diluc was scared. The fear that welled up within him wasn't caused by some monster or Fatui member, but by the sight before him that was worse than even the biggest mitachurl.
The camp they raided had been a bit more difficult than the average fight Diluc experienced on his nightly crusades. He was honestly glad that the yaksha had accompanied him that night, even if he would never admit it to anyone. However, Diluc was beginning to understand that the immense power Xiao had wielded to deal with their larger enemies came with a price.
Xiao was kneeling on the ground, still surrounded by the bodies of their defeated foes. His breathing was ragged, sharp groans of pain occasionally piercing though. Wisps of black mist swirled off of his body, as if darkness was physically trying to envelop him. The yaksha trembled and began to fall to the side as the little bit of remaining strength he had left his body.
Diluc easily caught him, worry for the other winning out against the protests of his tired joints, "Xiao? What's going on?"
Xiao hissed upon being jostled. When he opened his eyes they were bloodshot and his pupils were dilated into thin slits. He quickly closed them again and his voice was strained as he spoke, "You- have to get away. It's not safe."
"I'm not leaving you here like this," Diluc held Xiao's hand firmly as the other writhed in what seemed like agony, "You have to tell me what this is. I can't help you otherwise."
"Can't help," Xiao gritted out before letting out a cry that was bordering on a scream, "Have- to go."
"I already said I'm not leaving you like this!" Diluc said sternly. He felt helpless, unable to do anything but watch as the other continued to twist his body in anguish.
That moment felt as if it lasted an eternity, though it was only a few minutes, when Diluc began to hear music. A flute, to be exact, that sounded both far away and close by simultaneously. It seemed to be coming from the direction of Stone Gate.
When Diluc turned back to Xiao, it almost seemed as though the calming music was easing Xiao's pain. His pained cries quieted and he stilled. His breathing was still ragged but it seemed that whatever was causing his suffering had retreated for the time being. Soon after that, the music faded away and the pair were once again left in silence spare Xiao's stuttering breaths.
Diluc let out a relieved sigh, "What was that?"
Xiao shook his head, pulling himself out of Diluc's hold as he dispersed his spear that had clattered to the ground, "I don't know for sure, though I suspect it is Barbatos. He seems to have a habit of sticking his nose into my business."
Diluc raised an eyebrow. He didn't expect something like that of Venti, though after considering it for a moment he supposed it made sense. Those thoughts got put on hold, though, as he rushed to catch Xiao once again when the yaksha swayed and began to fall.
"Hold on," Diluc stopped him from trying to continue and put his arm behind Xiao's knees.
"What- what are you-" Xiao yelped when Diluc scooped him up into his arms bridal style, "Doing?!"
"There's no way you're getting back to the inn like this," Diluc said, leveling a stern look at the adeptus when he opened his mouth to argue.
Xiao crossed his arms with a huff, "You know any other human that did what you just did would have my spear at their throat by now."
"I do," Diluc hummed as he started walking in the direction of Wangshu Inn. He really did, too. He recalled the first time he met Xiao and the fight that had taken place. Even in this state, Diluc had no doubt that Xiao could pin any human with his spear in an instant.
They continued in silence for several minutes until Diluc had the nerve to ask the question that was nagging at his mind, "What happened back there?"
Xiao bit his lip, one of the miniscule tells that let Diluc know he was worried about something. He sighed, "There's a reason I don't let humans close. It's dangerous."
Diluc wanted to make a remark about the hundred other reasons Xiao had told him for why he didn't like humans, but figured it wasn't the time. He looked down at the other for a moment, "Why?"
"You know who I am," Xiao muttered, "The last remaining yaksha. Conqueror of demons."
Diluc nodded. He had done some reading as he began spending more time with the other. He knew Xiao's other name, Alatus, and what his job had been during the Archon War.
"You don't face that much pure evil or participate in that much carnage and come away unmarred," Xiao shut his eyes as if trying to keep the memories of such things at bay.
Diluc held him a little tighter.
"The rage of the gods I have fought over the centuries has left its mark on my very soul," Xiao furrowed his brows, face twisting as he bit the inside of his lip for a moment.
Diluc had a feeling that this was the most he had shared with anyone in a long time. From experience, he knew such things were hard after spending so much time alone. He wasn't good at comforting others, but he could try. Brushing his thumb over Xiao's arm, Diluc kissed his temple and spoke softly, "Take your time."
A tiny bit of the tension in Xiao's body released at the touch. He continued, "The four yaksha I fought alongside all suffered the same fate. They lost themselves to that hatred. One killed themself. Two killed each other. The last one disappeared."
Diluc's heart hurt at the thought of Xiao ending up like his fellow yaksha, but he said nothing as Xiao continued.
"It causes constant pain. Usually I'm able to fight off the divine hatred within me, but sometimes-" Xiao cut himself off, obviously unable to continue reliving his suffering. His voice was quiet when he spoke one last time, "That's when Barbatos has to intervene."
"I see," Diluc said, voice barely above a whisper. He didn't continue the conversation as not only did he know Xiao did not want to, but also because they were nearing the bridge to the inn. Diluc did not want prying ears listening in on the secrets Xiao struggled to let even him hear.
They said nothing as they took the elevator up. Diluc nodded quietly to the boss as he walked to the room Xiao often stayed in when he needed a place to go. Upon entering Diluc beelined to the bed and gently set Xiao on it.
It was as he reached to take of Xiao's boots that the yaksha pulled back, "I don't need your help."
"I know that," Diluc said while beginning to work the adeptus' boots off, "Maybe I just want to."
Xiao didn't argue anymore. He stayed silent, watching as Diluc finished taking off his boots and stood. Diluc smoothed his slacks out and bent down to meet Xiao's eyes. As always he waited for the slight nod of Xiao's head before kissing him softly.
Upon pulling away, Diluc brushed his thumb over Xiao's cheek, "I should probably head back to Dawn."
"Wait-" Xiao began to speak before cutting himself off, looking away with what seemed like the beginnings of a blush along his cheekbones.
"Yes?" Diluc raised an eyebrow, curious as to what request could visibly fluster the adeptus like this.
"I-" Xiao seemed to wrestle with himself for a minute before letting out a frustrated noise, "Stay- please."
Diluc glanced out the window and saw the moon hanging low in the sky. He knew he should head back lest anyone learn he had been out all night, but then Xiao looked at him and he knew what he answer would be, "Of course."
Suddenly the mood felt different somehow. Despite having been whatever they were to each other for a while, the pair hadn't shared a bed or even spent the night together before. Diluc couldn't help but feel a little nervous while he removed his jacket and boots.
As he took down his hair, Diluc felt eyes on him. He turned and gave Xiao what he hoped was a reassuring smile that didn't betray the way his heart was racing. The yaksha had situated himself under the covers and while adepti didn't often need to sleep, Diluc could see the way his lover was fighting to stay awake. What happened earlier had taken a lot out of him.
When Diluc finally slid under the soft sheets Xiao pressed himself against the his side. He curled up similarly to a cat, which Diluc found very endearing. It wasn't long until Xiao was fast asleep. Diluc, not quite ready to sleep, took a book that he had stashed in his patrol bag and began to read.
Around an hour later, Diluc felt as Xiao began to tremble against him. The adeptus let out a pained cry similar to what Diluc had heard from him earlier that night. Not sure what else to do, Diluc called his name and rested a hand on Xiao's shoulder.
Instantly, raging golden eyes with pupils slitted met his gaze as his wrist was held back in a bruising grip. Xiao didn't see Diluc in that moment, still deep in the battlefield from his memories.
Diluc held perfectly still, not wanting to provoke Xiao anymore. Before the adeptus could do anything else, Diluc did something neither of them expected.
Diluc began to hum, voice soft as he repeated the melody he had heard from the distant flute just hours ago. He continued to stay still, waiting for the other to come back to him on his own.
After a moment, Xiao did just that. His rapid breathing slowed and he blinked, eyes coming back into focus. Upon getting his bearings, Xiao realized he was holding Diluc's wrist way too tightly and dropped it as if it had burnt him.
They stared at each other for a moment before Xiao turned away, voice quiet and fragile in a way Diluc had never heard from him, "I shouldn't have asked you to stay."
"No," Diluc inched forward cautiously. He placed his hand on Xiao's face and brought it back to look at him, "I'm glad I stayed. Especially if it means I was able to halt your suffering."
Xiao looked down at the red marks on Diluc's wrist, "I hurt you."
Diluc lifted his free hand and moved it, showing that his wrist was fine, "This is nothing and you know that. It wasn't intentional and what matters is that you're okay."
"How can you just say that?" Xiao huffed, "I said it before I'm dangerous."
"No you aren't," Diluc gave him that gently stern look again, "You are more than a tool for destruction. You are more than the rage that you suppress."
"You are-" Diluc swallowed down the urge to run away that he often got when he truly let down his walls. Xiao needed to hear his honest feelings, "You are everything to me."
"Diluc-" Xiao tensed, not prepared for such a thing to come from his lover's mouth, "You can't mean that."
"Well I do," Diluc tucked a piece of Xiao's wild hair behind his ear and brushed his lips against the yaksha's forehead. He looked deep into Xiao's eyes, "So let me stay."
Xiao's voice was barely audible, trying desperately to keep it from cracking, "Okay."
Soon after that Diluc had Xiao tucked safely in his arms, some hope in the back of his mind that holding the yaksha could help stave off the nightmares at least for a little while.
"How did you know what to do?" Xiao asked upon realizing what song Diluc had brought him back with, "How did you remember it?"
"How could I forget?" Diluc replied, "I wasn't sure what else to do. I- I know it's not the same but if I can do anything to ease your pain I will."
"Can-" Xiao started but paused for a moment, embarrassed, "Can you do it again?"
Diluc couldn't help the smile on his face when he kissed the crown of Xiao's head, "Of course."
Xiao fell asleep to the sound of Diluc humming the ancient song with Diluc following soon after. That night ended up being the first one Xiao had slept through peacefully in centuries.