Specially for LupinandHarry...
A/N: All references to 'the host' mean the person who has been possessed by Riddle, just in case it isn't totally clear.
Interlude: The Chamber Opened
Tom Riddle was very smart. He had made his first Horcrux at the age of 16, a feat unprecedented in Wizarding history, something that could also be said of the relish with which he had disposed of his father. Once that had been taken care of, he had enhanced his Horcrux with several immensely complex enchantments, which he was still proud of many years after leaving Hogwarts, even after learning far more showy magic, even after becoming so feared that people refused to even utter his name. So no blame could seriously be attached to the person who had found his old school diary. They had been lost the moment they touched it, even that brief contact allowing Riddle access to their mind.
Everyone's mind is different. This is the first thing a student of Legilimency learns. It might be something natural, it might represent a man-made structure. Whatever it is, it will be something associated with security, safety. The mood affects it; a good mood will result in a beautiful landscape, or fairytale castle, or whatever the subject's mind resembles, whereas a bad mood will result in something from a gothic horror story.
This person was different.
When Tom Riddle had arrived inside his new host's head, he had seen their minds centre, a representation of something Riddle took to be his host's home. Several weeks later, and this mental fortress was barely recognisable. It had been ravaged, now looking as if it was about to fall to the ground. This was because, in a sense, it was. Riddle had ripped into his host's mind to create a secure hiding place. He had seen, even from a brief scan of some surface memories, that at least one person he knew to be a skilled Legilimens were at Hogwarts, and he could not risk discovery. He was now so firmly entrenched in the host mind that it could take months, possibly years to totally heal his host. Not that he cared.
Riddle had been waiting for this for weeks. The moment he gained consciousness inside the mind that he now called home, he had been aware that he had a unique opportunity. Dumbledore would never suspect his host of opening the Chamber, especially when he was well aware of the Heir's identity. His unfinished 'school project' could be resumed. One day after awakening, he had 'guided' his host into using the second floor bathroom, looking out from behind their eyes. He had been annoyed to discover that his last victim, Myrtle, had decided to haunt the toilet, but it wasn't an insurmountable problem.
Then he had heard about Harry Potter's invitation to the Deathday party.
Riddle had never been a particularly jovial person, but he came very close to dancing a jig when he heard this. Every ghost in the castle would be there, including Myrtle, and everyone else would be at the Halloween Feast! Perfect seclusion for his first trip to the Chamber; he couldn't have done better if he'd planned it himself – which given his prodigious cunning, was saying something.
He had his host feign illness the night of the Feast – serious enough to warrant bed rest, but mild enough to avoid interference from anyone. As soon as everyone had left, he took full control of his host's mind and body, heading straight to the second floor bathroom.
Sure enough, it had been empty. He was unable to suppress a slight laugh as he hissed at the sinks; it was so easy! Dumbledore really was a fool… The sinks split apart with a low grinding sound and a flash of white light, water pouring from the shifted pipes. There was a pipe to slide down, but that was hardly an appropriately dignified form of transport for the Heir of Slytherin; a Levitation charm was much better suited.
Riddle looked around as he moved through the murky passages miles underneath the school. Even here, little had changed. To Riddle, there was a curious beauty in the crafting; he could sense the subtle and clever magic that had been woven into the tunnels, shimmering gently to his powerful eyes. The ornate door to the Chamber was even more impressive, beautiful silver snakes that almost seemed alive, incredible jewels for eyes, and pulsing wards, again visible to Riddle's sensitive eyes only. The snakes moved aside, unlocking the door as they did so, when he hissed a command at them.
Riddle didn't pause as he walked into the Chamber, heading straight for the enormous statue of Slytherin in the centre. Kneeling in front of it, he hissed again:
"Speak to me Slytherin, greatest of the Hogwarts Four!"
The statue's mouth opened, and a noise came from inside. Riddle waited as the basilisk hidden inside uncoiled, slithering out to face its master. It instinctively lowered secondary eye-lids to prevent the person kneeling before it being turned to solid stone while still allowing it to see.
"It has been many years since I was released from this place, and you are not the one who did so last time. What would you have of me?"
"I am the same one who released you to feed all those years ago your majesty; I inhabit a different body for the moment, but rest assured my aims are still the same."
"I care not for your aims – I desire only food. It has been so long since I hunted."
"You can do so tonight. Muggleborns have plagued this castle for too long – I am going to eradicate this generation once and for all, and you shall have all the food you can eat! Rise to the surface, King of Serpents!"
The basilisk wound its way back to the pipe, following Riddle as he floated back up, both the serpent and the human hissing as they moved. Myrtle was still absent, but there was a noise from outside. Riddle walked to the door, his feet splashing in the pool of water, and opened it to reveal Mrs Norris, the caretaker's cat. She looked up at him, and arched her back, hissing. She backed away, and then the basilisk's gaze hit the water. Mrs Norris shifted to look at the new threat, and saw the reflection of the snake's golden eyes in the water. She instantly froze, stiff as a board, falling on her side.
Riddle worked forward to examine the cat. He was surprised at the Petrification; he had thought that nothing would happen unless one looked directly into the Basilisk's eyes – he would clearly have to be more careful. It wasn't as if he, or the body he was inhabiting, was immune to the deadly gaze if the eyelids weren't lowered. The Basilisk coiled around the pillars at the entrance to the bathroom, hissing softly to him, pleading to be allowed to feed. Riddle absentmindedly Transfigured a wall hanging into a dog, and the serpent lunged, snapping it up and devouring it. A cold smile crossed Riddle's face. The Petrified cat might actually prove to be useful. Moving swiftly, he picked it up, hanging it from a torch bracket. He then aimed his wand at the wall, carving a message into it with a blaze of fire:
Enemies of the Heir beware; The Chamber of Secrets has been opened.
As he stared at his work in satisfaction, he became aware of the sound of running feet. He turned to look down the corridor as someone came flying round the corridor – a young boy, maybe a second year at most. The boy shouted something, but Riddle couldn't be bothered to listen. Instead, he just sent a powerful jolt of magic towards the boy, sending him flying backwards several feet down the corridor. He strolled towards the prone body, bending down to examine him. He gasped as he saw the scar on the boy's forehead, and realised who the boy was.
Harry Potter. How ironic. Riddle was strongly tempted simply to blast the boy into oblivion there and then, but he had learnt what had happened to his older self, the great Lord Voldemort. Riddle wasn't about to make the same mistake, not until he knew why the boy had been able to survive. However, he wasn't sure how much the boy had seen, so there was really only one choice… He raised his borrowed wand and cast an "Obliviate" at the prone boy, altering the memory of his encounter. He didn't have time to do a perfect job – it would be obvious that his memory had been altered if anyone was rummaging around inside Potter's mind, but they would be unable to break the spell without causing serious mental damage, so strong was his spell. Turning back to the Basilisk behind him, he hissed once more, and the serpent obediently slithered back down the passage to the Chamber, ready for the next time Riddle called it.
For his part, Riddle ran back to his host's bedroom. The amount of magic he had used against Potter had tired him out, but that was all to the good as well. It would leave his charming host drained and weary as well, lending support to the story of illness should it ever be questioned.
As he ran, Riddle smiled. It was good to be back.
A/N: And on that seasonal note... I hope you all have a very merry Christmas!