Voldemort

• Potter!
  Dressed in a simple black robe, a petite young man with tousled black hair and round glasses with shiny metal frames stopped, surprised by the sudden call.
  “It’s strange,” he thought, looking around. “Who can talk when there’s no one around?”
• Uh, yeah?
  Something hissed in obvious irritation.

“Here, down below,” said the voice in a sarcastic tone, but with a certain mournful undertone.
Harry looked down. At Potter's feet, on the edge of the Forbidden Forest, lay a coiled, snow-white cobra, its front half erect, its hood fluttering proudly. The snake's pink mouth was slightly open, revealing its fangs. Although he had encountered a rather large and impressive specimen, upon closer inspection, Harry noticed that the cobra looked a little battered and very tired, despite its intimidation ploy. It should be noted that Harry still felt no fear of it, as, with the exception of the Slytherin Basilisk, he had never encountered a snake that had ever tried to harm him, and so he was not particularly frightened of the cobra.
Although, Harry had to admit that he hadn't encountered that many snakes in his life to make such a generalization about them.
Nevertheless, the boy crouched down to be level with the angry snake. Besides, he was an intrigued Gryffindor, which meant he sometimes did things that might not seem particularly smart.
"Um, you know my name," Harry said, confused that his brain had actually registered the creature's address to him as a tidbit of information.
The snake hissed again. Apparently it was a bit hot-tempered, but it still made no move to attack him.

• Of course I know your name, boy. I know everything about you, more than anyone else.
  Something in the snake's tone and mannerisms made a flash of recognition click in Harry's mind, and when he noticed the non-reddish-pink eyes,

Severus Snape, the Potions Master, and Hogwarts Headmaster Albus Dumbledore decided to eliminate their archenemy, the Dark Lord Voldemort, using an ancient potion that sent a person back to their weakest state. They hoped Voldemort would revert to a homunculus, but they were wrong; he became a cobra, which was essentially his weakest state. Now Voldemort must ask his archenemy, Harry Potter, for help, as he is the only one besides himself who understands Persentan (the language of snakes).
Will he succeed or not? It depends on how good he is at pretending to be a poor, unfortunate snake and how kind Harry Potter is.