Heads up to anyone who follows my TWD stories. This one is a Supernatural story.

I'm extremely new to the SPN fandom, but have fallen hard and fast! Please excuse any errors in canon (other than Destiel - that's non-negotiable!) – feel free to let me know so I can fix any problems.

Disclaimer: I do not own anything related to Supernatural. Wouldn't mind if I did, though...those boys are awfully cute.

"How many times do I have to tell you it ain't gonna happen!" Dean snapped over his shoulder as he picked his way through the thick underbrush of Purgatory's forests.

For the hundred and thirty-seventh time, Castiel tried to make Dean see reason. "I'm putting you in danger. You know the creatures here flock to me – you've seen it yourself."

"Life's a bitch, ain't it?"

"Dean!" Of all human experience, Cas felt he understood exasperation the most.

Dean grabbed a handful of Cas's trenchcoat and yanked him close, bringing them both to a stop. The slope on which they stood forced him to look up at Cas for once. "Look, I don't give a crap about that stuff! You're not leaving! And if you try? I swear to God I'll put a leash on you!"

"If you two would shut up for two seconds, you might notice that we're being stalked by one of those creatures right now," Benny drawled as he walked casually up behind them. "On the ridge across the wash. A shassi. I only see one."

Cas looked just in time to catch a glimpse of the beast as it crept along above them. Basically humanoid in shape, this one was clearly female and covered in long, bristling quills. A cold feeling crawled over him – shassi were uncommon, but more deadly than almost anything else they might encounter in Purgatory.

"I see it," said Dean as he released Cas and adjusted his grip on his blade. "Best way to kill it?"

"For us? Beheading," murmured Benny. "But watch yourself. She's quick and vicious and those quills? Mighty nasty venom – very ugly way to die."

Dean nodded. "Got it. Plan?"

"I have a plan," Cas announced, then took off running directly toward the creature, scooping up a fallen branch of suitable heft as he went.

"Cas!" bellowed Dean. "You stupid son of a- Dammit! Benny, come on!"

Castiel heard them crashing through the underbrush behind him, but he'd caught them by surprise, giving him what he hoped was enough of a head start. The shassi flattened herself on the ridge, muscles bunching beneath her skin as she readied herself to attack. It would be a close thing, but Cas was fairly certain he would be able to deliver a disabling blow before she killed him. With a broken limb or two, she wouldn't stand a chance against Dean and Benny's weapons.

The shassi launched herself from the ridge, and Cas readied his tree branch. But he'd miscalculated the stubborn determination of the elder Winchester. Dean tackled him from behind just as the shassi leapt, knocking him flat to the rocky slope and out of the creature's path.

But Dean himself was still too close. The shassi lashed out as she sailed past, and Dean screamed as her quills pierced his skin and tainted his blood. Shassi venom wasn't just deadly, it was excruciating. Cas watched in horror as it happened, helpless to stop the exact thing he'd been trying to prevent in the first place.

The shassi landed gracefully and spun around to face them, hissing. She reared up for a final strike. But in her focus on her injured prey, she failed to notice Benny behind her. He swung his blade in a long arc, and her severed head tumbled down the slope, coming to rest against a rocky outcropping.

"Dean!" Cas shouted. Prying Dean's hand away from the wound, Cas felt a glimmer of hope. The shassi's quills had only scratched the surface – there was a chance he might live. He turned to his other companion who was using his blade to nudge the corpse farther down the slope, away from where Dean moaned and writhed on the ground. "Benny, we need a place to recover – someplace sheltered that we can defend. We need it now!"

The vampire nodded, crouching down on Dean's other side. "We passed a cave not far from here. It might be the shassi's den, which would work to our advantage. Nothing sane will go near it."

Benny heaved Dean to his feet and dragged him back along the shallow wash. His vampire strength allowed him to keep hold of him despite his thrashing. He led the way to the cave, somehow managing to scramble over rocks and fallen logs without stumbling. As promised, the cave wasn't far, though it seemed to Cas to take far longer to arrive than it should.

The cave was at the back of a narrow draw, making it fairly well hidden. It was definitely the shassi's den. The ground was littered with bones large and small, and some of them were tied together with twigs and grasses and hung in the bushes and low branches of the surrounding trees – territorial markings. When they got to the cave's mouth, Cas eased Dean to the ground while Benny made himself a makeshift torch and scouted inside. Shassi were usually solitary, but it was possible a female could have a litter tucked away at the back of her den. He returned a few minutes later and gave a nod to indicate it was clear.

The two of them heaved Dean up again and dragged him inside. The cave was deeper than it appeared from the outside, the tunnel making a sharp curve to the right and opening into a slightly wider area, though the roof was still too low to stand up straight. The air inside was cold and earthy, but there was a hint of a draft, meaning there was enough ventilation they could have a fire.

Cas brushed aside the scattered bones to clear a place before they lowered Dean to the floor of the cave, as far back from the entrance as possible. Benny worked to build a small fire near the bend in the passageway and let Cas tend to Dean. The venom was working its way through his bloodstream now – spreading the agony from the wound in his arm to the rest of his body.

Dean thrashed, tossing his head side to side and crying out in pain. Cas took off his trenchcoat and bundled it beneath Dean's head to protect it from the stone floor, then sat beside him to endure his own kind of torture – being unable to help while his friend suffered. He reached out, carefully taking Dean's injured arm to examine the wound. Dean flinched and moaned at the gentle touch. It was difficult to tell in the flickering orange light, but the tissue around the scratches seemed to be swollen and red.

"Cas!" Dean ground out between gritted teeth.

"I'm here," he assured him.

"What the hell is happening to me?" His voice was raw with pain.

"It was the shassi. Do you remember? You were scratched by a few of her quills."

Grabbing Cas's hand in a crushing grip, Dean opened his eyes. They were glassy and fever bright. "Am I dying? It feels like I'm dying."

"It was just a scratch. You won't die, though you might wish for it before this is over,"

Face contorted again with agony, Dean growled, "Well, that's just freakin' fabulous!"

Benny made his way over in a crouch and set the water pouch beside them. "Fire's going. I'll bring in some wood before it gets dark and keep watch out front. You'll take care of him?"

"Of course."

The vampire leaned forward to grip his shoulder. "You know what's coming?"

Cas lowered his eyes. He knew. Looking up again, he nodded.

"Holler if you need help," Benny added softly before turning to exit the cave.

Castiel watched him go before turning his attention back to Dean who had fallen silent, but still shuddered with the venom coursing through his veins.

"Cas?"

"I'm here."

"What'd he mean? What's coming? Did something follow us? Is that hedgehog bitch still out there?" Dean choked the words out between panting breaths.

The angel touched a hand to Dean's forehead – he was hot and clammy already. It wouldn't be long now. "No, Dean. Please, just focus on getting better. You're safe here."

"Then what's coming?"

He paused, unsure whether it was better for him to know or if the fear would only make it worse. "The pain you're feeling now is just the beginning of what's coming." He sighed through his nose. "This will be unpleasant."

Dean's eyes went wide with horror. "You're saying this is the easy part?"

Castiel chose not to answer that, instead reaching for Dean's shoulder to support him. "Sit up, if you can."

Together they managed to get Dean up to sitting, and Cas helped him drink from the water pouch. The fever would dehydrate him, so he needed to drink as much as possible before he couldn't anymore.

"You're sure I'm not going to die?" Dean rasped after pushing the water skin away.

"I'm... Yes." Cas hoped that this was one of those times when white lies were appropriate. He was reasonably sure he wouldn't die, but didn't want doubt to cause Dean to be more afraid than he already was.

Suddenly, Dean gripped Cas's arm, and his face showed fresh fear instead of pain. "Cas, something's wrong. Something-"

He was cut off as he convulsed in a seizure. Cas threw himself forward, getting an arm between Dean's skull and the cold, stone cave floor. He caught him, wrapping an arm around the rigid torso and turning him onto his side. Cas lay down behind him to keep his arm protectively beneath Dean's head. He didn't try to stop the convulsions – just held him enough to keep him from injuring himself. And because he could do nothing else, he spoke softly in Dean's ear with the hope that it might soothe his fear and pain.

"Dean. I'm here, Dean. I know it hurts, but it will be over soon. I'll help you. Benny is keeping us safe, and I'm here with you. Everything will be okay." He had no idea if his friend could hear him, but figured it wouldn't hurt to try.

The seizure seemed to go on forever, with Dean rigid and convulsing against him. When it finally ended, Dean fell limp in his arms. Cas rolled him to his back, tucking the trenchcoat beneath his head again and smoothing his dirty, rumpled hair. Dean appeared to be only semi-conscious, and unaware of his surroundings, but he still shuddered from the pain of the venom eating away at his veins. With Dean's blade, Cas managed to cut a piece of fabric from his own shirt without disemboweling himself, then gently wiped away the foamed saliva that had trickled from the corner of Dean's mouth during the seizure. He rinsed the filthy, damp cloth with water from the pouch and dabbed it across his forehead in an attempt to help cool his fevered skin.

"Dean? Can you hear me?"

His eyes opened and tried to find him in the firelight. "Cas?"

Castiel breathed a sigh at his return to awareness. But then he realized that whatever Dean was seeing, it wasn't really there.

"Cas? Cas?" Dean struggled against his own uncooperative body in his sudden panic. "Cas!"

Cas placed a hand on Dean's chest to keep him from trying to get up, but had to dodge a fist when Dean took a swing at him. He caught the flailing limbs, preventing any more attempts to lash out.

A spasm arced through Dean's body, and he cried out in pain. When it subsided, he looked around wildly with fevered eyes, still struggling against Cas's restraining hands. "No, don't! Sammy! You can't- I won't- No! NOOO!"

The anguish in his cries caused a terrible ache deep inside Cas's chest. "Dean, it's Castiel. Can you hear me? You're sick, but I'm here to help you. Dean? Please, don't fight me."

Sweat poured down Dean's face, and he shuddered through another wave of pain, but stopped struggling so hard. "Cas? Help me, Cas!" Tears filled his unseeing eyes. "It hurts! Please, it hurts! Cas?"

Castiel placed a hand on Dean's burning cheek, turning his head to look into his eyes. "I'm here. I know it hurts – I would give anything to be able to take the pain away, but I can't. You'll get through it. I'm here with you."

The deep green eyes finally seemed to focus on his face. Dean's hand came up to grip Cas's wrist. "Cas, I need you. Please don't leave me. Please?"

The plea tore at him in places he didn't know could hurt. Cas knew that every second he stayed with him in Purgatory greatly increased the chances of Dean's death, and if that happened – if Cas were the cause of Dean dying... Castiel couldn't bear to consider it. It couldn't be allowed to happen. But right now, Dean needed him close.

"I won't leave you."

"Promise me," Dean demanded. And when Cas hesitated, he barked, "Cas, promise me!"

He nodded. "I promise."

Suddenly, Dean stiffened again, his head snapping back to thud against the meager padding of the trenchcoat as another seizure took him. The tendons in his neck stood out starkly as his body strained against itself. Cas put an arm under his shoulders and heaved Dean up enough that he could sit behind him, pulling Dean between his legs and up against his chest on his side. One arm held Dean in place against him, while his other hand smoothed his hair.

He continued his rambling monologue from before. "I promise, Dean – I won't leave you. I'm here. You're safe. You're sick right now, but we're keeping you safe, and you'll be better soon. I'll take care of you. I'll always take care of you."

It took longer after the second seizure for Dean to be able to speak, but by then he was lost in fever dreams. He writhed and shook, screaming at people and monsters who weren't there. Castiel held his burning body close and murmured softly to him, trying to soothe his terrors.

All at once, Dean tensed, but it wasn't another seizure. He stared fixedly at a single spot of nothing, shivering in fear.

"Dean, it's okay."

"No," Dean gasped out. "No!"

"What you see isn't real. You don't need to be afraid."

His friend shrieked and struggled, clawing at him to get free. Whatever he saw, it frightened him badly enough that he was struggling to get away from it. Cas had no idea what could make a Winchester run in fear, but he was grateful it wasn't really here.

Incoherent in his delirium, Dean howled and snarled and fought against the arms restraining him. But Cas held on and kept trying to talk him through his fear. Eventually, the fight went out of him, and Dean was reduced to whimpers and twitches. At long last, he fell still other than the sharp panting breaths and the shivering that never seemed to stop.

Several hours into the ordeal, as Dean slept fitfully in Cas's arms, Benny came in to check on them and add more fuel to the dwindling fire.

"How is he?" the vampire asked softly.

Cas looked down at the mussed and sweaty head resting on his chest. "I believe the worst of it has passed. He will be all right. Eventually."

"Need anything?"

Castiel asked him to dampen the filthy hunk of cloth he'd used earlier and leave the water within reach for when Dean woke. He dabbed the wet fabric over Dean's forehead and the back of his neck. He was still too hot, but not burning up like before.

"Thank you, Benny."

The big man nodded solemnly and returned to his post outside.

In the quiet that now dominated the cave, Cas listened to Dean's ragged breathing and considered how lucky he'd been today. One more quill or a deeper scratch and Dean could easily have been taken from him. The thought made him tighten his arms around the hunter.

Tipping his head a bit, he could look down and see Dean's face where he rested against his chest. His breathing was still rough, but the pain seemed to have eased somewhat. His eyes moved behind his closed lids, making his eyelashes flutter in a way that shouldn't have been notable, but it was, nevertheless. Cas watched his shifting lashes and the other tiny tics of his face in fascination. All the dirt and scrapes and bruises they collected in Purgatory never seemed to diminish Dean's beauty in the slightest, though it did hide the freckles sprinkled across his nose, which was somehow disappointing. Cas touched the hair at the back of Dean's head, stroking it softly and rubbing the short strands between his fingers.

Dean made a soft sound in his throat – an odd cross between a sigh and a moan – and a strange sort of heat rushed through Cas's body. He frowned. He was certain he had not come in contact with the creature's venom, so his vessel couldn't be developing a fever.

Just then, Dean stirred, though his eyes remained closed. "Cas."

"Dean. How do you feel?"

Clearly not awake yet, Dean nuzzled his cheek into Cas's chest, and didn't answer.

Another disturbing flush of heat washed through Castiel. That he felt no pain further confirmed that the strange sensation couldn't come from the shassi venom, but he didn't know what else it could be.

Pushing the concern aside for the moment, he returned to his observation of his sleeping friend. His breathing had eased and the shivering had finally stopped. Cas pressed his palm to Dean's forehead, then his cheek. It appeared his fever had broken some time in the last hour as well.

Castiel shook out the wadded up trenchcoat and flung it clumsily to drape over Dean. Despite the fire, the cave floor was cold, and Cas needed to keep Dean warm now that the fever was gone. He pulled him closer against himself to share what body heat he could.

Benny came to check on them a few times during the night, but they were otherwise undisturbed, for which Castiel was grateful. Uninterrupted sleep was the best thing for Dean's recovery, and Cas didn't mind his new duties as pillow and heat source. In fact, once Dean's pain had subsided and he was no longer in danger of death, Cas found holding the hunter this way quite comfortable. He'd stopped worrying about the warm surges that came now and again, like when Dean mumbled in his sleep and snaked an arm around Cas's waist. It didn't appear to be dangerous to him after all, and once he got used to it, he actually found the feeling quite pleasing.

Dean woke with a start. "Cas?" he asked blearily, fumbling a bit as he tried to make sense of where he was.

"I'm here, Dean. How do you feel?" Cas asked.

"What's going on? Why am I-" He suddenly went very still. "Uhhh, Cas? Is that an angel blade in your pocket or are you just happy to see me?"

"I'm very happy to see you, Dean. I'm pleased you seem to have recovered. Very few creatures have ever survived shassi venom."

Dean pushed himself up to sitting, and Cas had to catch his shoulders to steady him.

"Wait, 'survived'? What the hell happened to me?"

Castiel picked up the water skin. "First, drink. You're dehydrated after your ordeal. Then I'll tell you whatever you cannot remember. How do you feel?"

Dean wavered unsteadily as he took a long drink from the pouch. "Okay, I guess." He rolled his shoulders experimentally. "I'm sore, though. And dizzy."

"Then you should rest," Cas said, reaching to bring him back to his chest.

"Uhh..." Dean hesitated. "Why was I..." He gestured uncomfortably at Cas.

"You needed to be restrained through the seizures and hallucinations for your own safety, and after the fever ended, it was the best way to keep you warm."

"Through the-" The hunter shook his bleary head. "Okay, fine. But start talking. Tell me what happened."

As Dean settled stiffly against his chest, Cas asked, "Do you remember the shassi? There was a fight."

"A fight." Dean was quiet for a moment as he sorted through his memories. "I remember there was a fight, but after that it's just...nightmares."

"We were stalked by a shassi. During the resulting confrontation, you were scratched by some of her quills before Benny killed her. We brought you here to recover." His voice dropped to a whisper as guilt clogged his throat. "We were very lucky. If you'd been scratched by more quills or if the scratches were any deeper...you would most likely be dead."

Dean didn't comment, and Castiel felt the need to fill the silence. "Your nightmares were partly real. The venom causes excruciating pain, fever, and seizures – usually followed by death. But you were strong enough to pull through."

"If these shassi are so deadly, why haven't I heard of them before?" Dean finally asked.

"They were eradicated from the earth almost as soon as mankind learned to use weapons from a distance. Humans have a tendency to kill anything they fear, and these creatures gave them much to be frightened of. Just as vampires have been hunted nearly to extinction, so it was with the shassi. They exist only in purgatory now."

"Well, thank fuck for that," Dean growled.

Unfamiliar with that expression, Castiel declined to respond.

Gradually, the tension bled from Dean's body until Cas thought perhaps he'd fallen asleep again, which was good. Getting as much sleep as he could would allow him to recover more quickly, though it would be at least a few days before he returned to full strength.

But Dean wasn't sleeping. "Cas?"

"Yes, Dean."

"Why did you do it?" His voice was tight. Strained. Like when he was upset.

Puzzled, Cas began, "I don't know what y-"

"I remember, Cas." Dean's fist was bunched in Cas's shirt, and his body thrummed with tension again, though he hadn't moved from where he rested against Cas's chest. "I remember you running right at that shassi thing even though you knew – you knew – it would kill you."

Castiel didn't like the roiling in his stomach that this discussion was causing. "Dean... I'm sorry. Shassi are quite deadly. I was trying to keep you from danger, and instead I nearly got you killed."

Dean shoved himself away, and knocked aside Cas's hand that reached to steady his swaying as he sat up. "Are you kidding me? That's what you apologize for?"

"I'm sorry, Dean. It was my fault, but I was trying to keep you safe. I would do anything to keep you safe."

At first, Dean just stared at the angel in disbelief. Then he abruptly clasped Cas's face in his hands and pulled him into a rough kiss. It wasn't elegant, but the feeling behind it was raw and powerful. Castiel's head swam and his whole body flushed hot. Dean broke the kiss as roughly as he'd begun it, but kept his hands where they were, forcing Cas to meet his eyes.

"Dammit, Cas, you idiot! I'm not mad at you for almost getting me killed. I'm mad at you for almost getting you killed!"

Dean's eyes burned into his, but Castiel could only blink at him in confusion.

"Now you listen to me, you feathery son of a bitch, and you listen good. You will never, EVER do anything that stupid again, do you hear me? If you-" He broke off as his voice cracked. He clamped his mouth shut, lip quivering with the effort of holding the rest back.

"Dean..."

The hunter cut him off with a shake of his head. "No. Never again. I need you, Cas. I need you with me, and you promised. I remember that, too. You promised you wouldn't leave me!" Tears escaped and made trails through the dirt on his cheeks.

Castiel ached knowing he'd caused these tears. All he wanted was to make Dean happy and keep him safe, and now he'd failed at both. He reached up slowly to touch Dean's jaw, running his thumb along the sharp angle to catch the rolling teardrop.

"I won't leave you," he promised again.

Dean released his hold and broke eye contact. "Damn straight, you won't."

Cas immediately missed Dean's touch. Unwilling to lose that connection, he leaned forward until their faces were just inches apart. Dean appeared startled at first, but he didn't pull away. His respiration increased the closer Cas got, and just before their lips met, he pulled in a sharp, jagged breath. Then his eyes fell closed, and he kissed Castiel, bringing his hands to cup his cheeks once again.

Inexperienced as he was, Cas mostly let Dean lead the way, and quickly decided he wanted to learn more about this physical form of affection. He'd finally associated the pleasurable heat sensations with Dean – his touch, his voice, and now, his kiss. Warmth flooded him once again as their lips learned how to move together. A light and fluttering feeling filled him – almost like wind rustling through his wings, but on the inside.

When Dean's tongue swept over his lower lip, Cas's heart rate soared. He parted his lips to let Dean explore his mouth more fully. The moment Cas grew bold enough to flick his own tongue outward, Dean made that sound again – that sighing moan that ignited a hotter, more focused fire low in Cas's abdomen.

Suddenly, Dean broke the kiss, breathing heavily, and tipped his head to rest their foreheads together. "Cas," he breathed.

And then he slumped against Castiel who caught and held him tight as he'd done the night before. He twisted to look down at his friend's pale face. "Dean, what's wrong?" he asked, fearful that this was some aftereffect of the venom.

"It's okay, man. Just dizzy is all. Still weak." He gingerly shifted himself to rest more comfortably against Cas, head on his chest. After a while, he asked softly, "Cas? Are we- Is that what you want?"

"Yes. I care deeply for you, Dean. I would be gratified to have another means of expressing that to you." He looked down at the hunter and added, "Also, it is quite pleasurable."

Dean tipped his chin up to meet Cas's gaze. "Now you're talking my language!" The gleam of humor in his eyes shifted to something far more difficult to identify. "I... care about you, too, you know."

"I know. Your actions tell me that every day." Cas frowned as he realized suddenly that his own actions had told a different story. "Dean? I am truly sorry for what I did. I never meant for you to be hurt."

"You dying would hurt me a lot worse, Tree Topper."

Cas tipped his head. "Tree Topper."

But Dean gave him no explanation. Instead, he nestled against Castiel with a smirk, closed his eyes, and drifted back to sleep.

A/N: Bonus brownie points to anyone who recognizes the inspiration for the shassi.