Colin sighed. He was tired from a long day at work, far too tired to be taking a lengthy hike through the woods on his way home. Normally he enjoyed the peaceful walk. The wooded area was small enough that he wasn’t likely to come across any bears but large enough to experience that back-to-nature feeling he’d so often craved. However, it was getting late in the day, and he was a little wary of traveling the path. Still, the risk was less than taking public transit, so he took his chances. 

He could see the beginnings of the full moon rising over the tree line and smiled at the sight. He liked watching the moon, seeing how it illuminated the landscape. As a child, he’d always been a sucker for werewolves, even wondering from time to time what it might be like to be one, a night at a time. Just to run and hunt and howl and escape his shitty life every once in a while. He smiled from the nostalgic feelings the sight of the moon brought with it. Maybe this would be an enjoyable walk home, after all.

He spent the walk with his head up, enjoying the view of the setting sun in the distance and the oncoming night. If he hadn’t been looking up he would have missed it. As he watched the sky he saw something moving across it faster than he would have expected. At first, he paid it no mind, figuring it was just a plane. But it was soon moving too fast, too low, too small for that. 

Colin squinted into the sky, seeing a bright shape whizzing past, getting alarming closer the more he stared. He blinked at the object in the fading sunlight, trying to make out what it was as it sped closer and closer. Too late, he realized it was headed for him!

Colin ducked down as fast as he could, though was surprised when nothing actually hit him. He heard a crash some feet away, in the bushes just past the walking trail. He breathed a sigh of relief. That was too close a call! 

Curiosity won out and Colin figured he’d take a look to see what had hit. It was so close, after all. Maybe it was some sort of debris?

He came upon a smoking crater, only a few feet wide, yet still enough to make a noticeable dent in the ground. He stepped a little closer, wondering if it was something that had fallen out of a plane. It happened sometimes, he’d read. He considered calling a local news station to report it. It wasn’t big news, to be sure, but they might appreciate the tip. 

Colin stared into the crater for a few moments, surprised to see nothing in the hole. The reddish glow made him think it was a meteor or some other kind of rock. It must have exploded on impact. He sighed. He figured he might as well leave. There was nothing of interest here. And besides, the sight was creeping him out a bit, reminding him of the plot of too many horror movies. 

As he started walking away, he noticed he was stuck, as though his foot had sunk into the ground. He tried again to lift his foot but it was cearly trapped. Yet it hadn’t been raining recently and the ground had not been noticeably muddy during his walk. What had caught him?

Colin tried lifting his foot again and gasped, realizing that something was crawling up his shoe towards his pants. He pulled with all his might but failed to move his foot even an inch. He couldn’t even get his foot out of his shoe! 

He yelled as he felt something cool and slick touching the flesh of his leg under his pants. Panicking, he tried to pull whatever it was off with his hands. It felt cool and fluid, yet none of it came off as he grasped at it. It continued to run up his skin, leaving him feeling stunned. The grip on his shoe had let up but he couldn’t move his right leg! 

A moan escaped his lips from a surprisingly arousing sensation crawling up his groin. Colin felt himself pound erect as it passed his junk and started to move up to his stomach. He could scarcely fathom why he was getting hard at a time like this. But, he couldn’t deny the erotic feeling as blood pounded painfully into his groin, making him leak precum from the suddenness. 

Yet the arousal was a distant second when, suddenly, his heart, his lungs, and everything else stopped moving, leaving him entirely paralyzed. All he could do was yell for help as the goo, or whatever it was, began settling into his chest. He barely had any feeling in his lower body! 

Colin shuddered as the substance started melting into him, squeezing in between his skin at the cellular level. The goo was slowly entering his body! Soon, he couldn’t even see the goo anymore as every ounce seemed to dissipate into his skin. The whole process took several minutes, leaving Colin very confused, and much to his surprise, still very aroused.  

He fell forward as the paralysis slowly wore off. He felt… strange, as though something was inside of him. There was a strange tingling that he couldn’t place. Colin wasn’t sure if it was the goo inside of him causing it, or if maybe he imagined the whole exchange. 

Colin lifted his shirt, checking his chest for any signs that something, anything had entered him, violated him. Nothing. The only proof he had was his rather insistent boner, which he was ashamed to realize would not abate. 

Colin gathered his things, preparing to walk back home. He couldn’t think of anything else to do. It had been an unbelievably strange night thus far, and he was eager to get back into the monotony of his routine. Yet, all of a sudden he felt a massive pain in his head. It was as though something was inside him, trying to assert itself over him. His mind flashed back to the horror movie scenario from earlier. Oh, SHIT, it IS an alien!, his mind screamed as he fell to his knees, clutching his head. 

<Do not struggle, human. I won’t hurt you. In fact, you can consider me a gift. A gift to you, one who is compatible with my DNA. What luck! My first human, and I no longer need to search further!>

Colin grasped his head from the painfully loud voice that nearly split his eardrums. Yet, nothing outside of him seemed to be causing the noise. It really was just something inside of his head!

The voice kept droning on that painful tone that he could hardly conceptualize. Colin started tearing up from the unbearable pain. He wasn’t sure if it was the presence of a fucking alien in his head, or something else. Whatever it was, it was leaving him in agony!

<My… emm… apologies, human. My intrusion does cause momentary discomfort. But it will pass. There, see! Already my voice is not so abrasive! Soon we can discuss the important matter of our new mutual arrangement!> 

“Get the fuck out of my head!” Colin yelled,  ignoring the fact that the pain in his head was indeed starting to wear off. It was reduced to a slight headache as the alien spoke once more.  

<Such an interesting species. Always resisting the promise of something new. Why is it that you immediately assume hostility? True, the bonding process was made without your consent, but that was an unfortunate necessity. I have no way to communicate with your kind in my natural state, you see.>

“Get out! I don’t wanna be controlled! I won’t help you!” Colin screamed, the plots of a dozen sci-fi films racing through his head. He wondered what he had to do to get rid of the intruder. He hoped he wouldn’t have to hurt himself or anything, but was willing to sacrifice himself if need be. That had to be better than allowing the beginnings of an alien invasion! There was a hospital not too far away; maybe he could get help there? 

<Controlled? No, no. My presence is not meant to be a parasitic infection, human. It is more of a symbiosis. I’ve entered your body and intend to live here safely, as I can not exist on your planet without a host. I have no intention of controlling you, or, in fact, interfering with your daily life in any way. Unless you do something that would impede your survival and in turn, my own, of course>

<In return I can afford you certain benefits for putting up with my presence. Physical enhancements, as it were. I have the ability to convert you into something tailored to your particular desires. A quick look through your thoughts is all I… yesss… that will do, most perfectly.>

Colin stood up, confused at the being’s words. Convert him? What did he mean? He didn’t want to change to suit this creature’s whims!

The voice answered as though reading his thoughts as quickly as he had them. <It is true that I can change your form into one more suited to my metabolic needs but… well, I have just the thing in mind for you. It’s written all over your thoughts like a book. The process is easier to show you than to try and explain it. Trust me, I think you’ll appreciate this.>

Colin stood there for a long moment, the voice silent for the time being. He still found himself wondering if he was hallucinating the whole thing. Had he inhaled something from the meteor that was causing him to go crazy? 

Figuring there was no use standing here, Colin started walking again, absently scratching at his itchy arm as he went. Something felt off about the texture. He felt a patch of thick hairs at his touch, much more than he had been just moments ago. And the hair almost felt… soft? 

Colin looked down in shock to see an expanding patch of grey hairs. They were spreading over the backs of his arm and moving towards his hand, where they began to turn white. He was puzzled for a moment as he watched the hairs grow and multiply. The grey hairs were a contrast to his usual brown ones, looking out of place on his arm. In fact, they almost reminded him of a… no, that couldn’t be possible, could it? 

Colin felt his fingers subtly begin to ache and watched in fascination as his nails started to darken before his eyes, almost as though he’d been wearing nail polish. They began to thicken, to lengthen, getting pointed as Colin looked on. His fingers were lengthening as well, white fur spreading on them as the entire diameter of his hand began to expand. His palms felt unnaturally rough and he turned them to see that his skin was bubbling up, thickening and darkening into the beginnings of what looked like canine paw pads!

The fur continued spreading up his arms as the muscles underneath bulked and bulged with new mass. How was this happening? The alien must have been altering him on some microscopic level. Was that what it meant? There was no other clear explanation, save for hallucination.

Colin moaned as the muscles in both his arms bunched up, adding a level of definition that was far greater than anything his human body could ever hope to support. His arms looked comically out of place on his frame as they continued to grow, the fur spreading slowly up them and covering him in a soft coat above tough skin. 

He could feel his pecs bulging as they expanded against the fabric of his increasingly-tight shirt. Colin grasped at it with his claws as he tried to get it off over his head. Yet, his now-lupine digits tore it off with a resounding rip. Colin would normally have minded such a thing but was instead fascinated by the sight of his pecs bulging, his fur peppering his chest into a thickening treasure trail. 

He watched with rapt attention as all the fat on his belly seemingly evaporated. Eagerly, he rubbed his hand over the firm hard-packed muscle forming there. The muscle continued to writhe and expanded, forming the start of a sizable six-pack of abs the likes of which he’d never imagined on his form! He was handsome as fuck!

The grey fur continued covering Colin like a wave, gray safe for a triangular patch of pure white fur on his chest. Yet, of most note was a strange black spot forming on his shoulder. It looked almost like a paw pad… just like… but no, that was impossible, wasn’t it? How could anyone else have known about that? Unless…of course…the being inside him had access to his thoughts, his memories. And it had chosen a form that was exactly as Colin had always wished himself to acquire!

<I see you figured it out. Your race can be so… disbelieving, sometimes. It was the perfect form for you based on your memories. And now you will be able to access it at will. In exchange for housing me in your body and allowing me to exist here on earth, of course. A small thing to ask, really. Do you accept my terms?>

“Y-yes! Fuck yes!” Colin yelled as he felt the changes begin to accelerate. 

His pants tightened around his waist as they began to tear in some places, exposing thick patches of grey fur. There was no time to remove his shoes before his feet began rapidly expanding against the weak leather. He moaned a little from the confinement as his growing paws sank into the leather. New claws tore apart his socks while his expanding heels burst out the backs of the confining shoes. 

His lupine-hybrid feet grew larger, his toes splaying as his large toe rotated up his leg. Their soles grew hard and calloused with that same thick black skin that adorned his palms. Colin moaned again, more in pleasure this time as his lupine feet popped apart the weak leather shoes and were finally allowed to breathe in the moonlight.  He kicked away his shoes triumphantly, glad to be rid of the unnecessary humanity. 

His head ached as the fur began running up his thickened, bulging neck. Itching assaulted his face and he rubbed at it with his paw, feeling masculine stubble growing out into a thick beard before softening into lupine fur. A dull ache erupted as his face began to push outwards, taking his blackening nose along with it. Gums itched and bled a little as his teeth grew long and pointed. He blinked a few times as his eyes watered, knowing full well they were deep blue without even having a mirror to see them.

The changes swept away the remains of Colin’s human visage as his forehead sloped and his muzzle extended to proper length. He must have been three times the size of his former human self and was still growing! Ears grew longer and pointed, stretching with the alterations to the shape of his skull. He quickly found he could twitch them on their own. Though he didn’t have a mirror, Colin knew that the tips were adorned with white fur. His human hair melted into the gray ruff on his neck, its thicker presence giving him a handsome mane.

The world came alive with lupine senses as his changes reached their climax. It was as though he had been blind all his life, but suddenly he could see! His eyes could detect the tiniest fragments of light in the dark corners of the woods. His ears could shrivel effortlessly, picking up sounds for miles, be it prey animals nearby or the distant sounds of humans going about their evening activities. 

And his sense of smell was beyond compare! The world exploded in a multitude of scents that Colin’s new wolfish mind was only beginning to unravel. Not only could he distinguish the scents of every rock, tree, and beast surrounding him, but he could also detect life that had passed through days ago! It was as though the world was painted over with a history that only he could read.

One pungent odor stood out above all the others, however, sparking particular attention in Colin’s changed psyche. It was one that spoke of need, of lust, sending further shivers through his already-needy loins. It was then that Colin realized he was still powerfully erect through the entire process. 

Careful of his new claws, Colin shucked off his underwear in time to view the changes in his painfully erect member. Thus far, it was the only aspect of his that retained its humanity. He moaned as his cock continued to lengthen, its tip pointing while its base thickened into a fat canine knot at. His balls were rapidly covered in soft gray fur, and Colin could see the skin around his head pulled down into a lupine sheath towards the knot he now sported. Colin almost drooled at the sight of the perfect lupine member he sported. 

<I know you’ve been wanting to, Colin. Go ahead. Enjoy all my gift has to offer you.>

Colin wasted no time, grasping his reddening member in his paw hand as a wave of euphoria washed over him. He didn’t know if it was the alien directly controlling his pleasure centers, or if his body was truly this sensitive, but he didn’t care. The sensations from stroking his lupine rod were everything he could have ever imagined and more. 

<There, you see? A mutually acceptable from. I have a greater protein requirement than your species typically consumes and this body will help us achieve that goal. Nothing sentient, I can assure you. Simple prey species will suffice. No different than taking making from your grocery stores, though objectively more direct.>

< I should inform you, once I have settled on the initial change I can only make minor alterations to it. I can not change you into multiple different forms any longer. But, I take it you’re happy with the choice I made?>

Colin could only respond by stroking his fully erect lupine member. His entire body shook in delight at the changes and power that his new form gave him. It was like a dream; he felt as though he was floating away from himself, the powerful sexual energies almost too much for the human side of his brain to process. Thankfully, the being in his head had provided him the instincts and drives of a beast in rut. Colin allowed himself to give in as he stroked his rocket faster and faster. His rough paw pads gripping onto his cock tightly and allowing him a range of pleasure he’d never thought possible. 

Colin moaned as his furry balls began to tighten and churn with the massive load that he was so close to blowing. He knew he couldn’t hold it back much longer and he didn’t want to. In some ways, his bestial ministrations were his way of showing solidarity with the alien being in his mind. He wanted this, wanted to keep feeling this good. He readily welcomed a being into his body who could change him into a werewolf form whenever he desired, the fulfillment of all his darkest fantasies. 

He was so close. He couldn’t hold it back anymore as he felt his furry balls tense up and his cock throb as the pool of pre leaking from it grew steadily thicker. He was going to cum! He needed this, more desperately than air or water. He was thankful for the alien presence and the gift he had been given and was ready to show it by exploding out of his massive member with a joyous cry. Almost there… yes… it was happening!

“AAAARRRRRRRROOOOOOOWWWWWWWWWW!”

Colin howled as his balls shook and his massive red rocket shot spray after spray of thick lupine cum all over the forest floor and his hand paw, marking this space as his. No, theirs, he corrected himself. The alien in his head and he was one now. 

He stood there in a post-orgasmic release, his paw and the ground soaked in his lupine essence. He had never felt stronger in all his life. He panted, allowing the cool night air to wash over him, relieving him after that intense workout. But even after all that, his body still felt energized, ready to explore, to hunt. These woods would not be enough, but he knew that another treeline boarded near here, an expanse of woods that would satisfy even his new appetite for exploration and sensation. 

There was still one small matter on his mind he wanted to address before tending to the new needs of his body. “Rhat should I rall you?” Colin asked aloud, knowing the being in his head could hear. 

<I think you already know the answer to that, Colin. The perfect name is already here in your memories. From henceforth, you can refer to me as Thunder.> replied the voice, seemingly equally as happy in aiding Colin to achieve his dream. A happy host was the way to achieve true harmony, after all. It would ensure that the being could continue to exist in the new world it longed to explore.

“Thunder. Rees, that name suits us,” Colin said, playing around using his new muzzle for speaking. It took some effort, but he was at least able to reduce the guttural canine quality of his tone somewhat.

With that, the new creature called Thunder ran out into the night, eager to sample it all had to offer. Both beings were excited with the prospect of perceiving the world with their new senses. They were to experience life in a way they had both only dreamed of until now. It was going to be a true symbiosis, after all.