Fiery Light by TemporalPhoenix



Summary: While visiting the planet Cosylian, the Doctor accidentally inhales toxic spores. A number of unpleasant effects ensue, ranging from painful hypersensitivity to hallucinations. Speaking of hallucinations, is that really Rose Tyler in the TARDIS, or is she just another figment of the Doctor’s fever dreams?
Rating: Teen
Categories: Tenth Doctor
Characters: Rose Tyler, The Doctor (10th)
Genres: Angst, Hurt/Comfort, Romance
Warnings: Swearing
Challenges: None
Series: None
Published: 2021.07.21
Updated: 2021.07.26


Fiery Light by TemporalPhoenix
Chapter 1: Lost in the Fog
Author's Notes: I watched the documentary Fantastic Fungi and was amazed by all the versatile properties of and uses for fungi that I had never known about/considered before. Somehow, that led to this story....which depicts a very unpleasant, murderous fungus that totally doesn't illustrate how adaptive and useful many fungi on Earth can be. I think the fact that most of this story was written in 2020 had something to do with how it turned out. It's definitely a little bit darker than I originally intended, but-- Oops. Spoilers.

It was one of those days when the Doctor’s great, big, superior Time Lord mind decided to be an utter bastard. No matter what he did, no matter how many people he saved or which planets he explored, his thoughts always returned to the hellish grief and loss he had suffered through in his 904 long years of existence.

These sorts of days didn’t happen as often when he wasn’t alone, he knew that all too well. He knew better than to travel alone for too long, for fear of what he’d become without someone there to stop him and remind him of what he’d promised to be. Yet here he was, traveling alone, letting the universe get to him, and absolutely nothing was going right at all.

The Doctor was jerked out of his morose thoughts when his shoelace caught on the limbs of a low-lying shrub and he went crashing to his hands and knees. He yanked his shoelace free from the offending plant and ducked as a poisoned dart whizzed past his right ear, embedding itself in the trunk of a nearby tree.

With barely another moment’s pause, the Time Lord scrambled to his feet and took off running in search of the TARDIS again. The planet Cosylian was fast becoming less of a pleasant, semi-tropical distraction, and more of a big mistake with a significant chance of causing another regeneration.

The Doctor was sure the TARDIS was somewhere in this particular section of temperate rainforest. He’d parked her no more than a kilometer or two from the edge of the Northern Continent’s capital city, Rhessyc. Ergo, she really shouldn’t be hard to find. He knew where he had landed and could sense his ship’s presence like he always could— as a comforting telepathic hum in his mind that had been there for far longer than it hadn’t. Unfortunately, the underlying bond he shared with the TARDIS didn’t help him pinpoint her location any faster.

He put on a new burst of speed when he heard the sound of numerous darts embedding themselves in the rainforest floor right behind him. He had long since engaged his respiratory bypass for a number of reasons, which became something he was deeply grateful for the moment he ran straight into the middle of something far more problematic than the squadron of guards chasing him.

The ground beneath his feet suddenly grew spongier. Magenta moss and indigo soil gave way to pale blue sand and dust that stood out in stark contrast against the deep blues, purples, pinks, and reds of Cosylian’s fertile rainforests. A white-blue mist burst from the ground in swirling opaque wisps that instantly coated everything they touched.

The Doctor jerked back, stumbling away from the cloud as fast as he possibly could. (And for the 15th time that day, he was reminded that nothing about his visit to this planet had gone the way he'd planned.)

Cosylians from the Northern Continent called it the fog of death. Eastern cosylians called it the plague of sorrow, or simply “last sorrow”. Southern cosylians called it the “demon that dissolves the mind”. No matter the name it was given, the fog, the mind-dissolving demon, or the last sorrow, it was a type of fungus endemic to the planet that spread underground in thick, viscous tendrils, releasing massive clouds of spores upon receiving a certain amount of pressure. It didn’t take much to set it off. A single heavy footstep was more than enough.

The fog’s spores had powerful hallucinogenic properties. The hallucinations were said to drive victims mad within hours of inhalation, in addition to causing intense physical hypersensitivity and pain in the process. Of course, all of that came before the hapless victim finally collapsed from fever and suffocated to death. And if they happened to collapse on top of any patch of fog fungus, well…

Being slowly digested by the only actively carnivorous fungus in the universe on some backwater planet was not something the Doctor had ever considered when he thought about what might cause his next regeneration. He gave an involuntary shudder, quickly forcing the thought out of his mind.

At the sound of the guards still running full-bore through the rainforest toward him, he threw a panicked look over his shoulder as he continued to back away from the fog.

“Don’t come closer! It's the fog of death!” he shouted.

The guards skidded to a halt in a flurry of limbs and a clatter of their armor, designed to resemble a common Cosylian tree bark. The guards watched the Doctor with great uncertainty, not sure if he was bluffing or not. However, the instant they glimpsed the cloud of spores behind him they swiftly began to back away.

With one potential crisis temporarily averted, the Doctor took a moment to scan the ground around him with his sonic screwdriver. The results made his eyebrows shoot up in alarm. "Oh, wonderful. Of course, out of all the places in the entire forest..." he muttered. He knew he should have returned to the TARDIS the same way he’d left. In his mad dash back to his ship, he’d ended up more than a mile east of her. Most of that mile was completely taken over by the fog of death.

A scream behind him made him whirl around. Horror flooded through him when he saw one of the younger guards look down just in time to receive a face-full of deadly spores. Two other guards were caught in the same cloud, though less directly. The others scattered, shouting as they ran for their lives.

“Back away! That’s an order!”

“What do we do?”

“BACK AWAY, I said! Return to Rhessyc and alert the commissioners.”

“It’s the Time Lord’s fault! He probably knew this patch was here!”

“How did it get so big? I swear it wasn’t like this yesterday!”

In that instant, the Doctor knew he really, really shouldn’t have come to Cosylian. These people had been happily living their lives, recovering from a series of civil wars and content to deal with the scourge of the fog of death as needed. In blundering his way into trying to help them eradicate the fog, his presence had only caused more death.

There was no complete cure for the particularly persistent effects of the fog of death yet. No way to fully stop the toxins in the spores from spreading throughout the lungs, blood, and central nervous system if high quantities were inhaled. There were a few half-effective measures that could be taken, but only if exposure had just occurred, and the amount of spores the victim came into contact with was limited. The guards in the forest would not be so lucky.

Of course, it didn’t help that the Doctor had managed to offend all of Rhessyc and half the leaders on the World Council of Cosylian in one go with his “disrespect for the Mother Goddess” before he could learn what the half-effective measures against the fog actually were.

He swept the sonic through the air again, turning in a slow circle so he could get a full scan of the surrounding area. His hearts sank when he saw the results.

52.47% fungal-based organic matter detected in the soil composition, spreading out from a general origin point for over three kilometers. There was only one thing that could be. The fog of death, spreading faster than ever.

The infected guards’ screams were shifting from panicked to pleading. The Doctor exhaled shakily. Their hallucinations were setting in. He’d had no idea it would happen so fast. From what he’d gathered from the locals earlier that day, he thought it was supposed to last for many tortuous hours.

He was the Doctor. He had to do something, at the very least doing what he could to ease the guards' suffering. Rose would have wanted him to. Besides, he had a respiratory bypass, and could therefore survive contact with the spores without inhaling them, at least, not for a certain amount of time. He would eventually need to breathe, but not for a good long while.

He inched toward the infected guards who were rapidly succumbing to the fog. Gritting his teeth, he forced down the sickened feeling that rose in his throat as he watched them claw at their own skin. They coughed and choked, utterly unable to expel the spores from their lungs.

The captain of the guards caught the Doctor’s arm before the Time Lord could go another step closer. “Stay away from them. It is too late. We must escort you back to the capital," he ordered.

The Doctor wrenched his arm out of the captain’s grip, ignoring the way the cosylian’s sandpaper skin tore at his coat. “There might still be time to save them," he insisted. "Surely there's something I can do. I’m a doctor!"

The captain only shook his head. “I cannot allow you to go any closer.”

The Doctor bared his teeth in frustration, turning back to the infected guards with a growl of disgust. They had started begging, reaching out to figures only they could see with whimpering pleas for help they would never receive. The Doctor felt so very useless standing there, unable to help, yet too stubborn to run from the sight of the guards’ slow and painful deaths.

“Their minds are lost to us now. Anyone who goes near them could be infected next. We must leave them to the demon," the captain said, new urgency creeping into his voice as the spores continued to spread through the air.

The Doctor clenched his jaw, a fierce need to fix the situation still coursing through him. He made his decision. “If you let me go back to my ship right now, I can analyze the spores much faster than if I used any lab in Rhessyc. I might be able to find the right formula to block out the spores just fast enough to prevent the loss of their brain function. I’m sorry I offended your Mother Goddess, but I really can help! You just have to let me."

“Many have tried to create such a formula. It is a nearly impossible feat, even for our best scientists.”

“Yeah, but none of them were me," the Doctor snarled, frustration finally boiling over, “I’m sort of a genius, and I have a brilliant ship that could determine the necessary antifungal formula in a heartbeat if you’d just let me go! Look, just— Oh, come on! You can come with me!” With that, he whirled around and stalked away from the captain, the sonic already humming to life in his hands. He needed to find the clearest possible path to the TARDIS.

The captain sent his few remaining troops back to the city with orders to alert the governing body of their fellow guards’ fates, and that the captain had the Doctor back in custody. The Doctor nearly scoffed when he heard that. The cosylians could never hope to hold him in any of their primitive prison cells for long.

There was a quiet squelch of damp soil behind him as the captain caught up, falling in step with him. “Do you truly believe you can discover what almost no one else has been able to discover?” the cosylian asked.

The Doctor wasn’t in the mood to provide comforting reassurances, but he was certain about this. “Yes.”

“If you find the formula and help us make the first doses of it, than I will personally oversee your release. My only condition is that your formula works on the next victims of the fog, and that you will stay to make sure there are no significant negative effects from it. Then you will be free to go.”

The Time Lord made a noncommittal reply, not overly concerned about any such formula made by him not working.

The head guard remained insistent. “Do you agree to these terms?”

“Yes, yes! Now will you stop talking and let me concentrate? This fungus is hard enough to detect without your blathering.”

The captain went silent, focusing on pushing through the semi-tropical foliage. They had to move fast; the twin suns were beginning to set, and neither the Doctor nor the captain of the guards wanted to be out in the forest at night. The locals believed in and feared many demons and gods that supposedly protected and haunted their forests after dark. The Doctor had a growing suspicion that most of those vengeful deities were actually based on characteristics of the fog of death fungus.

It wasn’t long before the captain spoke up once more. “Which type are you scanning for?” There was a distinct tremor of fear in his voice.

The Doctor came to a grinding halt, rapidly turning to face the cosylian. “I’m sorry, did you just ask what type? I’m scanning for the fog of death, same as I have been for the last four and a half minutes.” His tone was passably incredulous, with an air of superiority instead of the anticipatory dread he actually felt.

The captain’s gaze fell to the sonic screwdriver. “There is more than one type of the fog, Doctor. Three types are most commonly found in this part of the world, each with their own dangers. For centuries we have dealt with them, eradicating the most ancient and deadly variants over time. But the others that survive, adapt, as I’m sure you know all things do. They come back stronger.”

“Why didn’t you tell me there was more than one common type before?" the Doctor demanded, his impatience fully giving way to burning ire. He just wanted to fix this problem as soon as possible, and leave Cosylian behind for the rest of time. Was that really too much to ask?

The captain regarded him coolly. “You did not know this before, yet you still believe you can discover a formula to stop the hallucinations and fevers of the fog’s victims?” he asked. The Doctor opened his mouth to tell him that of course he was sure, but the captain held up a dark, callused hand. “You involved yourself in our affairs, we did not ask for your help. You have caused trouble simply by being here. We are not in your debt"

“Even if there are three subclasses of the fog, there have to be similarities between them. They’re the same species. I can work with the one here, and analyze the other two later," the Doctor insisted.

The captain’s eyes drilled into his. “I hope so, for all our sakes.”

“Just watch me!” the Time Lord snapped. Then his breath caught and he looked away. He was trying to help these people, not push them away with bitterness and anger. “I’m sorry. I— I really do want to help,” he mumbled.

The guard captain bobbed his head in acceptance. “I believe the three fogs are distinct enough that you might be able to detect specific indicators for each. I will tell you all I know about each of them once we get to your ship. It is not safe out here in the wilds at night.”

“That just might work," the Doctor said. He quickly turned on his heel and began to scan the ground in front of them again. He moved at a slightly slower pace this time, with the captain right behind him. Now, the Time Lord adjusted the settings on the sonic as he went, to compensate for subtle changes in soil composition that he thought might be due to the presence of a different variant of the fog of death.

They’d only gone a few hundred feet when the sonic began to detect something undeniably different about the growth of the fungus in the soil beneath their feet. This one difference made the Doctor freeze instantly, left foot hovering in the air in the middle of taking a step. He stared at the sonic, eyes widening as the implications of its results sank in.

Hearing the captain come to a stop behind him, and knowing what he would be asked, the Doctor forced the words out as calmly as he could. “About those subclasses of the fog…” he began. He didn’t dare move forward until he knew more.

“What have you found?” the captain asked, sounding more alarmed by the second.

“Do any of the subclasses, by chance, happen to grow at an exceptionally fast rate at night?”

The captain inhaled sharply. “Yes, just one," he replied, "the rarest and deadliest of them all. But it doesn’t grow here anymore, only a few patches survive in the south!”

The Doctor closed his eyes with a strained grimace. “Really?” he asked with forced nonchalance, setting his left foot down the way one might a bomb about to explode. “Because I’m picking up on, oh, about 73% more fungal growth in the soil ahead of us than I detected in the same area fifteen minutes ago. It changed so slowly over time, I didn’t think to check for changes in total fungal mass. I was only scanning for new growth directly in our path.”

The captain muttered a curse under his breath. The Doctor looked apologetically over his shoulder at the guardsman and saw that his skin had paled significantly under his armor.

“The Creeping Night grew fastest in the dark, under the right conditions,” the captain said. “It used to suffocate whole towns in two nights or less. It is the worst demon of them all. Every city on the planet banded together fifty-seven years ago to find every single patch of it and destroy it. Before that, things were so bad that whole towns were dying within days of each other. Scientists like my grandmother worked day and night to find a way to stop it.”

“Your grandmother worked to stop it? Did she find a way?” the Doctor demanded, mind racing as he tried to piece every bit of the puzzle together as fast as possible. He was all too aware that they had, at most, a few minutes of safety left if they stayed in their current location.

The captain’s eyes darted around them, looking for any sign of the fog. “Yes, she did. Once the last civil war ended, every tribe on the planet started reporting deaths from a new type of fog that could spread and kill in a quarter of the time it took the others. If it has returned, we must inform the World Council immediately."

Doctor’s grip tightened around the sonic screwdriver. “I agree. Just tell me one more thing. How was the Creeping Night eradicated the first time?”

The guard captain’s breathing sped up in the face of his people’s worst nightmare. “A chemical spray was created to kill it while still preserving the rest of the wilds. My grandmother was there when the formula was discovered. It happened late one night. She and another member of her team had a vision of The Golden One, our Mother Goddess. She appeared before them in a burst of light. She spoke strange and beautiful words, looked at my grandmother’s friend’s notes, and altered them. After the vision ended, my grandmother and her colleagues tested the altered formula, and it worked. They saved us all. But that’s not possible now, not in this time."

That final comment struck the Doctor as odd. “Why is it not possible?” he asked. “What happened to that chemical and the notebooks with the original formula?”

“Both were destroyed in a fire years ago. We’d already stopped making the chemical before that, because it doesn’t work well on the other types of fog. They adapt too quickly. How close is the fog?”

“Can’t you just figure the formula out again?” the Doctor pressed.

The captain shook his head and asked again, “How close is it?"

The Doctor pointed the sonic at the ground in the direction of the TARDIS for a moment, then glanced at the readout. He winced. “We’re now five and a half feet away from the edge of a very large patch of fog, possibly the Creeping Night. It’s growing so fast. The patch is currently 16 feet across, 22 feet wide, but it used to be a foot smaller in diameter just two minutes ago. The only ways around it are blocked by trees or smaller patches of a different fog subclass. We can’t possibly walk between them without triggering all of it, and—”

“And behind us?”

The Doctor’s breath caught in his throat. Oh, he was so, so stupid. He twisted around and slashed the sonic through the air, scanning the ground they had crossed only minutes before. ‘Still clear for now, but…’ The Time Lord repeated the motion, this time aiming at an area a few feet to the right of their trail.

There it was. New fungal growth in the topsoil, spreading faster than any such organism he’d ever heard of or encountered before.

The universe was clearly NOT on the Doctor’s side today. His eyes darted back to the captain's. “You were right. We should retrace our steps, and run. Definitely run.”

They dashed through the twilight forest as fast as they could, with the Doctor leading the way and glancing at the sonic’s readout every few seconds to make sure the level of fungal growth directly ahead of them hadn’t changed.

The Creeping Night was growing so very, very fast. Impossibly fast. The Doctor wasn’t sure how he’d missed the initial growth of it before, because the sheer amount now was staggering. In the back of his mind, the Time Lord could feel the TARDIS humming with growing distress. She was surrounded by a few small patches of Creeping Night, and larger patches of the more common forms of the fog. Though the spores wouldn’t be able to breach her doors, she was concerned about her trouble-prone pilot. If he was overtaken by the fog, he might still be able to escape the forest before the hallucinations set in, but if enough spores entered his lungs, then he would be forced to regenerate. Of course, there was also the possibility that he might not make it away from the fog before that. (What a truly embarrassing way to burn through the rest of his regenerations.)

As if the universe had been waiting for him to think that very thought, the Doctor’s loose shoelace suddenly caught on a crevice in the side of a jagged rock half buried in the soil. He was going too fast to keep himself from ending up sprawled out gracelessly on the ground. The guard captain almost tripped over him in his haste before he skidded to a halt and doubled back, ready to help the Time Lord to his feet.

The Doctor sat up with a groan, silently cursing loose shoelaces and himself for not tying his properly. He waved the guardsman away. “Just keep going, I’m fine! We’re only—” He broke off, staring down at the pale blue dust coating the palms of his hands. He realized what was about to happen a second too late.

Greyish-white particles erupted from the ground beneath him, flying straight into his eyes, into his mouth through his parted lips, and up his nose before he could cover his face or hold his breath. He reeled back with a startled cry, coughing and wiping at his eyes with the backs of his hands. The sonic screwdriver dropped from his grasp, landing in the dirt beside him and causing another burst of spores to shoot into the air.

The Doctor felt his respiratory bypass kick in, but the damage had already been done. He’d inhaled more than enough spores to seal the fate of any Cosylian—especially if these were Creeping Night spores. And he could only guess how his Gallifreyan neurophysiology might react to them.

He heard the captain take off running, shouting an apology over his shoulder. The Time Lord didn’t dare open his mouth to reply.

He tried to get to his feet, but fell back to his knees when the action ignited his nerves with a sharp stinging sensation that was so intense it nearly made him gasp.

Where had that come from? He was stronger than this! It should be easy for him to dampen his pain receptors enough to push through the first stages of the fog's effects. Where was his bloody control over his own body?

‘Have to keep moving.’ He forced himself to focus, listening intently for the quiet hum of the sonic screwdriver. Once he’d pinpointed its location, he snatched it up and stuffed it into his coat pocket. Then he cracked his eyes open, squinting at the shockingly thick cloud of spores that was slowly enveloping him.

The planet’s moons hung low in the sky to the north and east, all of them too small to provide much light. It was well after dusk now, and if there was one thing the Doctor had learned from the locals before nearly being arrested for disrespecting their Mother Goddess, it was that the jungles of Cosylian were extraordinarily dark at night. He didn’t know how dark “dark” would be to his eyes, but he wasn’t keen on finding out anymore than he had to.

He had to get up. Had to get back to Rhessyc and fulfill his promise to help the Cosylians. He could do it, he knew he could, if only— Oh hell, why had no one ever mentioned the nerve pain?! 

Wherever the spores touched his skin was starting to burn and tingle, sending white-hot flares zinging up and down his limbs and sparking behind his eyes.

He had a very bad feeling about where this process was headed. For now, he could only grit his teeth and force himself to stand, to put one foot in front of the other and hope the hallucinations and fever would hold off for a little while longer. This was not how he wanted to die—regenerate—whatever. (Still felt like dying every time, even if the essence of him lived on.) He still had so much he wanted to do and see with this body’s eyes. Still so many mistakes to make up for, and run from.

He stumbled through the cloud of spores, his clumsy footsteps only making more of them burst from the soil. His vision went blurry for a moment, and he fell sideways into the trunk of a tree. He looked down, frowning at his empty hands and his white trainers that were slowly turning the color of ash. Where had he put his sonic? Why was the ground so…so…fuzzy? No, not fuzzy, it was blurry. And his hands, which were turning a very interesting shade of reddish-orange, were still empty. Why had he stopped moving again?

‘Ah, right. Sonic screwdriver. Must find that.' The Doctor plunged his hands into his coat pockets, fumbling around for the device. His left hand finally brushed against it and he pulled it out, only almost dropping it twice before he managed to turn it on.

He started walking again. The sonic kept swimming in and out of focus in his hand.

'There must be a safe route somewhere,'he thought desperately. There had to be.

On another note, his chest was burning. Now it wasn’t just his skin that itched, burned, and stung unbearably, but his lungs as well. It was quite distracting.

The Time Lord was just about to let out a long-awaited exhale when he remembered why he shouldn’t do that. ‘Respiratory bypass. Can’t breathe yet, still in the fog of death. Death and the dead and a regeneration I don’t want. Right. Keep moving. Avoid spores.’ He repeated the list over and over again in his mind, to force himself to stay on track.

(All those names for the fungus were starting to sound far more appropriate now. Very literal, but appropriate. Like…a warning label. BEWAREFog of Death, fatal to anyone who touches or inhales it.)

Maybe if he washed the spores off he would feel better, and less like he was burning. If he washed the spores out of his eyes, then they wouldn’t water and sting so much. Everything wouldn’t look so blurry. Then he could get out of this nightmarish jungle.

To do that, first he would need to find water.

No, that wasn’t right. First, he needed to get out of the fog and find the TARDIS.

The Doctor took another step forward, then another, and another, trying to brush the spores off his clothes as he went. Sonic screwdriver all but forgotten in his grasp, he staggered blindly through the night.

Something was wrong with him. Very, very wrong. He couldn’t seem to think properly. He had scores and scores of impressive Time Lord neurons in his brain. If those neurons weren't working properly, then...

Then...

A problem. That was a problem. 

With each step he took, the mist of spores in the air grew thicker, and the pinpricks of pain bursting into existence all over his skin gradually transformed into spikes. The Doctor did his best to keep going, really, he did. He told himself he had to get back to the TARDIS, had to find the guard captain, had to not give into the hallucinations if and when they started. He couldn’t keep a shuddering breath from leaving his lungs as he pondered exactly what he might see or hear.

It was quite dark in the forest now, even for his Gallifreyan eyes. He sputtered and coughed, and the fire in his lungs and throat only burned even hotter.

Darkness crept in at the edges of his vision. He blinked lethargically, peering through the clouds of spores.

Was that someone else wandering through the jungle? He was sure he’d seen someone walking toward him just now. Hopefully it wasn’t the guard captain. Whoever they were, maybe they could help him. Maybe the two of them could escape together.

Or maybe he was starting to see things.

The Doctor closed his eyes for what felt like a mere second, suppressing the all-consuming urge to cough that rose in his throat and hoping with all his might that the vision would go away.

He wasn't quite sure how he ended up on the ground after that. He only knew that when he opened his eyes again, his cheek was pressed into the infected Cosylian soil and he was breathing in more spores by the second. He coughed violently, spitting out all the spores he could and cringing at their dusty, bitter taste.

The forest blurred and spun, tilting around him in a dizzying dance. His skin itched horrendously, but scraping it against the soil only made him itch and ache at the same time in an endless, intensifying cycle. After another failed attempt to scratch away the awful itchiness, the Doctor gave up and let his eyes slide closed. He just needed a moment….then he’d get up and….keep....keep going….

He coughed again, curling in on himself as his body was wracked with the futile efforts of his respiratory system to clear his lungs and throat.

“Doctor?”

He choked.

‘No.’ His blood ran cold, and he vaguely registered the small whimper that escaped him. ‘Anything but her. Not today. I can’t bear it.'


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