This is for Aenigma's "The Child of Serpent" challenge listed on TheSilverSnitch which goes a little somethin' like this:
Harry was abandoned by the Dursleys at the tender age of four, and a magical serpent took him in and brought him up. He grows into a wild child that only understands parseltongue, wants to be a real snake and dislikes human beings in general. And when he decides that a certain Dark Lord should be his prospective mate,all Hell breaks out.
# The magical serpent that adopts Harry, it could be literal a magical serpent, or it could be a basilisk, a cockatrice, an occamy, a tatzelwurm or even a runespoor, whatever you like if it takes a snake form or was part-snake.
# Harry has to learn to become an Animagus - whether by himself or from the others - and he chooses his animagus form to be a silver, or maybe black, serpent.
# Voldemort would think Harry is just an unknown species of poisonous snake and take him as his new pet at first.
# One scene in which Harry fiercely defends his master (or mate), whether be it physically or verbally - the former one was most likely but not absolutely - and whether in his animagus form or not.
The boy wriggled his way down the tunnel following the little voices.
The tunnel widened suddenly and the voices stopped.
"Hello?" The boy hoped he hadn't scared whoever they were away.
The voices started again, but they were high-pitched and panicky. He wished he could see, but it was very dark this far underground.
"Please don't be scared, I won't hurt you!"
"Who are you," one of them asked.
He had to think very hard. He knew he had a name, but he had heard it so rarely. "I'm Harry."
"Hairy? That's a funny name."
Something rubbed against his hand, making him jump.
"Well you do have hair, so I suppose it fits," the voice added.
"Who are you," Harry asked.
"I am Scales."
"It's nice to meet you Scales."
Harry heard a soft hiss. The other voices had been silent during their exchange.
"I wish I could see you. Are the others still here Scales?"
"Certainly. This is our nest and we are waiting for the one who hatched us."
"Oh…Are the others your brothers and sisters, then?"
Scales was quiet and then, "Yes. Clutch mates."
"May I stay here for awhile? It's dark outside and I'm sleepy."
The other voices protested, sounding scared.
"Silence!" Scales shouted, as well as such a small voice could shout. The others immediately obeyed."Do you eat eggs Hairy?"
"Only if my Uncle gives them to me."
Scales was silent for a moment. "One of our clutch mates has not yet hatched, you will not eat her."
"Of course not!" Harry was shocked.
"Then you may stay until our mother returns. She will decide."
"Thank you, Scales."
The little voice didn't reply.
Harry moved into the cavern carefully. He could stand up but his hair rubbed in the dirt of the ceiling so he went back to his knees. He stopped when he found what felt like a large pile of feathers and sticks.
The little voice was right next to Harry in the pile. "Are you a bird?"
Harry heard all the little voices hissing and he thought it sounded strangely like laughter.
"No Hairy, we are Syrens."
"What's a Syren?"
Scales didn't answer so Harry lay down, curling into a ball for warmth.
"Are you a bird?"
"No Scales, I'm a boy."
"I have never seen a boy."
"That's okay, Scales. I've never seen a Syren, and my Uncle says I'm not a proper boy anyway."
The little Syren was again silent so Harry laid his head back down.
Harry woke when something tickled his face. Roughly he rubbed his hand over the spot and sat up.
"I am here Hairy. Our mother is also here and she will speak with you now."
"My hatchling tells me you desire to stay in my nest."
Harry bit his lip. "Yes."
"My nest mates said I couldn't stay with them anymore. They said they didn't want Dudley catching my freaky-ness."
"Sometimes things happen when I get mad or when I cry. One time all the dishes in the kitchen broke at the same time when I was crying in my cupboard."
"Ahhh. You are a Wizard."
"A person who can do magic."
"Yes, and you must be a special Wizard indeed to speak the snake-tongue."
Harry absorbed this new information.
"Are you a snake then?"
"Of a sort; Syrens are a mix of bird and snake, but mostly snake."
"Oh...So may I stay with you?"
"Yes young one."