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Published:
2026-01-30
Updated:
2026-03-09
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4/?
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Cold-Blooded

Summary:

At four years old, Harry Potter learned that humans hurt, but snakes just hide. So he stopped being human.

Now he's eleven—technically. In reality, he’s a python with PTSD, a Parseltongue-only vocabulary, and a neurological inability to remember how legs work. When Hagrid kicks down the door, he finds not a boy, but a traumatized reptile who hasn’t walked, spoken English, or been warm in seven years.

Enter Severus Snape, who did not sign up to be the foster guardian of a dissociated snake, and yet here he is: setting warming charms, prying Harry out of ventilation shafts with Wingardium Leviosa, and discovering that his new ward communicates exclusively in hisses that sound suspiciously like insults.

Year One: Harry learns to walk again, befriends a Draco Malfoy who smells like "food" (and friendship), refuses to play Seeker, and saves the day via strategic biting.

Notes:

(See the end of the work for notes.)

Chapter Text

Freedom was for the snakes. 

The fall breeze whispered amongst the trees as little leaves lifted into the air, dancing upon an unheard melody. A young boy, bright green eyes and brown hair held a rake bigger than his own body. Tiny hands struggling to lift the tool properly. 

A portly man sat in a chair on the front porch, arms crossed, eyes fixated on the boy who was failing at the task at hand.

“Boy,” the man glowered, “Can you not even complete a single task I give you? How useless.”

The boy’s arms were sore, his small body not ready for labor. 

“Harry Potter, answer when I speak to you.”

Young Harry looked up at his Uncle Vernon, shaking. Whether from fear or from exhaustion, that was not known. “I—sowwy sir.” The boy pleaded, small lisp laying heavy on his tongue.

A snake slithered by, scales shimmering in the late sun, free.

Harry wished he could be as free as the snake.

Uncle Vernon stood, chair creaking as his weight released it from its shackles. “Speak clearly, Potter.”

Step by thudding step, Uncle Vernon came down the stairs. He towered over the four-year-old. Harry hunched into himself, waiting for the hand to come down.

Pain exploded from his head as Uncle Vernon grasped at his hair, lifting him up to eye level. The young boy gasped. 

“If I tell you something, you answer respectfully. No ‘sowwy’, no baby sounds. You are old enough to work your weight around here. Do you hear me?”

Young Harry struggled in the man’s grasp.

He wished he could be anywhere else.

Wished he could be anything else.

‘Child.’ A voice echoed. ‘Become one of us.”

A leaf blew past Vernon’s face. Weight shifted in his hand. Hair turned to scale. Bone crunching and forming.

Before Vernon knew it, he was holding a snake. Vernon screamed, dropping the snake. It hissed in pain.

“Harry?!” Vernon screamed. The snake nodded hesitantly.

“Petunia! Your nephew magicked again!” Vernon cried out.

Aunt Petunia came running.

Her eyes widened as she saw the snake.

“Monster.” she whispered in harsh tones.

I’m sorry. I didn’t mean to. I—I’ll turn back. I promise.” But Harry could not wish himself into a human form. And his aunt and uncle could not hear him.

The yelling did not stop. 

The toddler curled into himself. A small snake in a small minded family.

When hands roughly grabbed him, throwing him in a dim cupboard with a small heat lamp, he did not fight, only curled into himself tired.

The freedom he had wished for was not granted, and his torment only changed forms.

This is the story of a boy—or rather a snake that would one day save the wizarding world.

But that day was not today.

And Harry slept beneath the fake warmth he had been given.

 

***

 

Harry’s eyes slit open, luminous and bright green. His golden brown scales glowing beneath the heat of the lamp. Harry stretched his coils until they hit against the cupboard walls.

Harry hissed a sigh as dust flitted down from the staircase.

“Wake up, snake! It’s my birthday! I’m going to the zoo!” Echoed Dudley from above.

Right.

Dudley’s birthday. 

Harry rested his head upon the cold floor. Knowing the Dursley’s, they’d let him out for Dudley to show all his friends, then, he’d be locked up for the rest of the day.

Just as he thought, the cupboard door creaked open, the scent of roses and vanilla in the air.

Harry slithered out carefully, bowing his head so he didn’t receive any pain.

A hand wrapped around his neck, and he knew well enough to coil in the stout boy’s arms. Dudley grinned. “There, Potter, I need you to behave. My friends will be coming over after I go to the zoo. And they will want to see my cool pet.”

Like I’d be more interesting than your 36 presents.’ Harry flicked his tongue. Of course, Dudley could not understand a single word Harry had said.

Dudley proceeded to give Harry a meager amount of crickets before locking him back in the cupboard.

“Later, Snake.”

Harry sighed, at least the lamp was nice and warm today.

 

***

 

“I want to see!” A voice cried out.

“No, I want to see!”

Harry shifted, verdant eyes fixated on the door.

When it creaked open, light spilt in, followed by grubby hands.

The hands wracked against his scales, pulling them the wrong direction. Harry wanted to move, to bite, anything. But Dudley had a grip of his head in his hands, and that was a snake’s weakness.

Harry glared up at his captor and hissed. ‘Get off me you pig’.

Dudley flicked his nose sharply. Harry reeled. “What did I say about hissing?”

Dudley smiled at his friends. “Seems Harry isn’t being good today. Who's up for a round of kick the can.”

If Harry could pale, his face certainly would. Instead, his coils drew tighter on Dudley’s arm. Before Harry can fight it, he’s stuffed in a large glass can Aunt Petunia used in her horribly unhealthy meals. Harry tries to protest as holes are poked in the top, allowing him to breathe.

Harry did not want to go through this again. The sheer amount of vertigo and syncope he experienced would leave him weak for days.

Just as Dudley was about to step out the door, a letter slid through, gently falling to the floor.

Dudley set down the large can Harry was in to pick it up. 

“What’s this? To Mr. Harry Potter…cupboard under the stairs? Hogwarts?” Dudley crouched down to Harry’s eye level.

“Who would be writing to my pet snake?”

Harry heard Uncle Vernon gasp. “Dudley, where did you get that?”

Before Dudley can reply, Uncle Vernon confiscates the letter and the glass Harry is in.

“Go play outside, boys. I’ll—I will figure this out.”

Dudley and his friends thought nothing of it as they went outside to play.

Uncle Vernon set the large glass on the counter, holding up the letter. “This should never happen. You are a snake, not a boy. You hear me, Potter?”

Harry was growing cold, the glass seeping his warmth like ice. But Harry nodded respectfully. He didn’t care about the letter. He can’t even read.

“Good.” Uncle Vernon says, shredding the letter to pieces. Then, he releases Harry back into the cupboard. “Now stay there and be a good snake until we have any rats for you to chase.”

The door shut, leaving the heat lamp as the only light source.

Harry sighed.

He really didn’t care about the letter.

 

***

 

He really shouldn’t care about some letter.

That is, he thought he shouldn’t.

But Uncle Vernon was being tormented by them daily. More and more appearing from seemingly nowhere. This place—Hogwarts—was persistent.

Today was Harry’s eleventh birthday.

Not like anyone remembered it.

Instead, they were having a family dinner. Feasting off nasty, fatty meats. Harry much preferred crickets and rats to deep fried desserts.

Harry was just about to go to sleep for the night when a small knock rapped on the front door.

Lightning cracked, the knocking grew louder.

Knock.

Knock.

Harry lifted his head curiously. 

Uncle Vernon sighed. “I’ll get it.”

Footsteps thudded towards the door. Harry heard it open, but immediately slammed back closed.

“Nope. Nope. Nope. I am not doing this tonight!”

Then, the door flung open, and the cupboard door ripped free. Harry’s eyes widened, his tail shaking in fear.

A large, scruffy man with kind eyes bent over. “I’m lookin' fer Harry Potter?”

Harry hissed when the man looked at him.

“I could’ve swern Harry were human.”

Harry backed up as a hand reached out towards him.

“I got ye something. Fer yer birthday.”

A boxed cake was dropped in front of him, words scribbled on top—though Harry couldn’t read what it said.

“Now see here!” Uncle Vernon called out. But the hands of the large man only reached out towards Harry.

Harry was no small snake, but these hands doubled his size. So Harry did what all snakes do in fear—he struck. The man laughed heartily. “Now I’ve had me fair share of bites. But never from the boy who lived!”

Suddenly, Harry found himself picked up more gently than any person before. “Names Hagrid. I have the honor of bringing ye to Hogwarts. But it seems like you’ve animagicked yourself? Are ye stuck this way?”

Harry released his fangs and ever so slowly nodded.

Hagrid smiled. “Professor McGonagall will know what to do. Me other mission will have to wait.”

And before Harry knew it, he was being apparated out of the house and outside the borders of a large castle. 

“Welcome to Hogwarts Harry. Happee Birthdae.”

Hagrid set him down on the soft grass. Harry tasted the air—rain, stone, something ancient and magical—and coiled instinctively around the nearest warm thing he could find: Hagrid’s massive boot.

He wondered to himself, would this just be a bigger cupboard? 

 

***

 

“Professor McGonagall is out at the moment, as you should recall.” A dark haired man snarks. “Whatever are you doing here? Your mission to retrieve the brat and the stone. I do not see either, Hagrid. Just a snake in your tasteless beard.”

Harry curled tight against Hagrid and hissed. 

Hagrid laughed. “Now Harry, Professor Snape here is right. I forgot me mission. Snape, will you watch Harry for me?”

Snape sighs, holding out his hand. “Give the thing to me, you fool.”

Slowly, Hagrid unwraps Harry’s coils. Harry resists, but ultimately is placed in the professor’s arms. Snape raises an eyebrow. “Rather large for a pet.”

“That is no pet.” A voice calls out from the left. Harry turns and sees a wise wizard, with white hair and a long beard.

He looked familiar somehow. The man smiled at Harry. Not at Snape or Hagrid—at Harry.

Hagrid nods at the man and turns. “I best be on me way. Good luck, Harry.” He leaves without another word.

Harry quivers between the two strangers. “Thank you Snape for holding on to our dear Harry Potter for us.”

Snape glanced down at Harry. “Like father, like son, I suppose. Should I leave him with you, Dumbledore?”

“Set him down for a moment, if you will.”

Snape sets Harry on the cold floor. Too cold, Harry immediately goes towards the closest warm thing, Snape’s leg. “You idiot, I just set you down.”

Snape flicks his leg, flinging Harry off him. Harry lands with a soft thud in front of Dumbledore.

Dumbledore smiles. “Now Harry, this is just to confirm a theory. Alright?”

Harry nods.

“I believe you are experiencing maladaptive animagus transformation. Meaning, you have been stuck in your snake form, that you inherited from a parent. Is this correct?”

Yes’ Harry hissed. Though Dumbledore did not understand. Harry had hoped wizards could understand him. Unfortunately, that did not seem to be the case.

Dumbledore took it as an affirmation anyways, flicking his wand. Bones crack and shift, his form growing, limbs appearing. Until a small boy—smaller than should be for eleven—appears, with brown hair and sharp green slitted eyes. Scales speckled his face.

Harry falls flat on the ground, unable to remember how to use the limbs of his past self.

What’s happening?” Harry asks in confusion. 

Dumbledore hums in thought. “Parseltongue even in human form, inability to use his limbs, hmm. Yes, this all appears to align with maladaptive transformation. This rarely happens in cases of child animagus. You will eventually learn how to use both forms. But for now, I want you to remember what it’s like to be a snake.”

Harry focuses on his cold blood, the way his tail could coil around him, the scents so strong, heat so welcoming. Suddenly, his form shifts back into a snake.

Harry looks up at the two older wizards. One smiling, one sneering.

“Severus?”

Snape sighed. “Yes, sir?”

“Might I ask you to care for Mr.Potter until McGonagall gets back in a few weeks?” Dumbledore asked kindly.

Severus glared. “He’s a Potter.”

Lowly, lower than Dumbledore assumes Harry can hear, he whispers, “Do it for Lily.”

Snape snaps his eyes towards Dumbledore, then to Harry.

He sighs.

 “Fine.”

Snape holds his hand out to Harry. “Are you coming or not, Potter.”

Harry gladly slithers up onto the warmth of another, the floor too cold for him.

“Let’s go.”

 

***

 

The dungeon was cold. The rooms were colder. 

Harry was tightly coiled against the professor’s chest as they walked by each Slytherin room. Luckily, Snape was generous enough not to throw him to the ground out of disgust like Dudley might have.

When they reached a larger room—one with banners flourishing the frame—Snape walked in. He pulled out his wand and the fireplace was lit.

Snape set him beside the warmth.

“Stay here, Potter, while I find something acceptable for your consumption.”

Harry just basked in the warmth as Snape left the room.

But then Harry began thinking. The only time the Dursley’s had ever let him near the fireplace was the winter they took care of the neighbor’s cat. And the second Harry had relaxed, the cat had attacked. The Dursley’s had laughed themselves silly watching Harry writhe in the cat’s grasp.

Slowly, Harry looked around at the room. There were tall tables with potions, a mortar, leaves, and a knife. Towering shelves full of dark books Harry couldn’t hope to read. There was another door to the left— the bedroom, and a door to the right— the bathroom. Right beside the fireplace there was a cushioned throne of charcoal and ivory. An owl sat in a cage nearby.

Harry shivered not from the cold but from fear. He was with a wizard. The torment the Dursley’s had done to him will seem like play compared to what a wizard can do.

Carefully, Harry slithered away from the warmth, away from the trap, finding a hole in the wall big enough for a larger snake like himself to fit in.

It was cold—too cold. He didn’t like it. Spiders crawled across the narrow snake passageway.

But he followed it anyway. Better free than comfortable.

 

***

 

Severus Snape would not call himself a kind man. Nor would he even call himself a decent one.

But what he would call himself is practical, pragmatic, capable, and responsible. As such, when the headmaster had put in his charge an animagi snake boy, Snape had been sure to set a warm fire before retrieving consumable food for the boy.

Soon, he would talk to Dumbledore about registering the boy with the Ministry of Magic, as is required by law. But he would only do so once he was sure the traumatized child of James Potter was at least able to attend classes properly.

He would not stand for a snake attending his Potions class.

Snape had grabbed a few items of food: a mouse, a gerbil, some crickets, and some spiders. He had hoped that one of these would suit the snake’s taste.

As he returned to his room in the dungeon, he did not see a snake basking in the flames of his fireplace. Nor did he see a boy trying to figure out humanity. What he did see was a hole in his wall big enough for that snake to have gone through.

Severus Snape was not a patient man. And finding a snake was not on his itinerary.

Homenum Revelio” Snape cast with a flick of his wand. Snape watched the outline of a snake from behind a few walls. Snape’s eyes twitched. “I swear.”

And with that, Snape began tracking the boy.

 

***

 

The walls were tight, but the passageways were wide open for a snake Harry’s size. Harry slithered forked tongue flicking. His eyes had easily adjusted to the dark, and he had spotted stairs ready for scaling.

Just as Harry began to climb he heard the swish of a wand. “Wingardium Leviosa” 

Suddenly, Harry was flying backwards into someone’s arms.

Harry looked up with narrow eyes at Snape. He flicked his tongue at him. 

“You’re the one trying to run away.” Snape turned, heading back towards the office.

Harry is set back down by the fireplace. When he immediately tries to move, Snape hexes him. “You won’t be able to move until you eat your dinner. And—”

Snape pulled out a ring from a drawer. He muttered an enchantment, then slipped it on Harry’s tail. “You won’t be able to leave any boundary I set. Which, for today, is this room.”

Snape then lowered a plate of food as Harry glared at him. Snape glared back. “You don’t have to like me, Potter. But I have to take care of you. Correctly.”

As Harry looked at the large spread of food waiting for him, he decided he didn’t mind being cared for.

He hesitated for a second, tongue flicking, checking for poison. None. He took a small bite, drooling.

He definitely hated Snape. Though, it was harder to continue that sentiment after gorging on gerbil with a delicious crunch.