Plot to open the Chamber of Secrets

The plot to open the Chamber of Secrets was an event that first took place in 1943 and later in the 1992–1993 school year. The first plot started with Hogwarts student Tom Riddle locating Salazar Slytherin's legendary Chamber of Secrets and the monster within. It culminated in the death of another student, for which Rubeus Hagrid was framed, and expelled from school. The second plot started with former Hogwarts student Lord Voldemort, then known as Tom Riddle, relocating the Chamber of Secrets and the monster within. It culminated in the Petrification of several students and the almost-killed students Harry Potter and Ginny Weasley, for which Hagrid again was framed for, and sent to Azkaban. It all ended with Tom Riddle's memory destroyed and the Basilisk killed.

Chamber creation
The Chamber of Secrets was a enormous chamber built by the Founder of Hogwarts and Slytherin House Salazar Slytherin in the 11th century. The chamber leads from the Second-floor girls' lavatory down through a chute to a circular room. That room has a hole that leads into a large room that has a door at the end of the large room. You have to speak Parseltongue to open it. The door leads into the main chamber that is a very large room with a little swimming-pool at the end and a wall-statue of Slytherin himself. The mouth is used to hide an enormous Basilisk which only comes out when the Heir speaks to it via Parseltongue. On the long way to the end is built some snake-heads. There is also a way on the right that leads into a walk with another long walk and a short walk. They both leads to the main chamber. However, in 1992, the circular room have a lot of rat-bones, and the large room with the door at the end is crushed when Gilderoy Lockhart used Ronald Weasley's wand to perform the Memory Charm which backfired and caused a lot of rocks to block the way, and the same room had a Basilisk-skin.

Tom Marvolo Riddle a.k.a The Heir of Slytherin
In 1926, A half-blood wizard named Tom Marvolo Riddle was born (who would grow up to become the man known as Lord Voldemort), In 1938, Tom Riddle came to Hogwarts and was sorted into Slytherin, He learned about the Chamber of Secrets and Slytherin's heir and found out in 1943 that he was related to Slytherin and he plotted to purge the school of Muggle-borns and Half-bloods (all of the half-bloods, except himself).

First Stage
In 1943, while Tom Riddle was at Hogwarts School of Witchcraft and Wizardry in Slytherin House and explored the school he found out he came from Salazar Slytherin himself, he opened the Chamber of Secrets and waked the Basilisk inside. With this monster he terrorized Hogwarts, petrifying a lot of people and killing a Ravenclaw girl named Myrtle, and blamed Gryffindor boy Rubeus Hagrid for it. After what the school thought was the monster were scared away and Hagrid was expelled, the terrifying things ended.

Between Stages
In 1945, Riddle graduated from Hogwarts and teachers expected him to go onto become an employee at the Ministry of Magic and possibly become Minister of Magic, but he turned down the offers and worked for Borgin and Burkes. He poisoned Hepzibah Smith to steal his ancestor's locket and Hufflepuff's Cup, when Hepzibah made an outrageous remark about Burke buying the locket from a ragged woman, Riddle recognized the witch as his own mother. He disappeared from Britain for 10 years and in 1955, Riddle returned as Voldemort to get the job as Defense Against the Dark Arts professor. Voldemort's first rise to power begins after the job request is turned down and the jinx on the post is operated. Voldemort dies in 1981 in an attempt to kill Harry Potter, In 1991-1992, Harry Potter is accepted to Hogwarts School of Witchcraft and Wizardry, Voldemort, who is on the back of Quirinus Quirrell's (the current Defense Against the Dark Arts teacher) head, forced Quirrell to try to steal the Philosopher's Stone and kill Harry Potter if he can. This failed, and Quirrell died instead which forced Voldemort to leave the body and search for another way to get back to the wizarding world.

Second Stage
Before the next school year, Death Eater Lucius Malfoy distracted the Weasleys while they were shopping at Flourish and Blotts and slipped Tom Riddle's Horcrux Diary in the seventh Weasley's cauldron, After the first couple months, the memory of Tom Riddle took over Ginny and forced her to petrify several students, finally, Harry Potter found the diary, but Ginny stole it from him and then, she finally went down into the Chamber of Secrets, where Tom Riddle's memory came out of the diary and took human form, Harry traveled down to the Chamber and learned Riddle was Voldemort. "So this is what Dumbledore sends his great defender, a songbird and an old hat... Speak to me, Slytherin, greatest of the Hogwarts Four... Let's match the power of Lord Voldemort, Heir of Salazar Slytherin against the famous Harry Potter... Kill him"

- Tom Riddle summoning the basilisk

Riddle then summoned the basilisk while draining Ginny's life from her. Riddle made it clear that his new goal was to kill Harry Potter instead of the Muggle-born students since Ginny had revealed to him that Harry was meant to kill him in the future. There was then a battle and the basilisk was killed. Riddle tried to stop a dying Harry Potter from destroying his diary, but failed again.

Aftermath
After the battle Harry Potter with Dobby's unspoken hints was able to correctly surmise Lucius Malfoy's involvement in the opening in the Chamber of Secrets, with Albus Dumbledore surmising that Lucius slipped the diary to Ginny Weasley for the personal benefit of sabotaging the Muggle Protection Act her father Arthur Weasley recently proposed in the Ministry of Magic. As the diary lost it's magic upon it's destruction there was no sufficient proof for these allegations, though Lucius did lose his position as a Hogwart's school governor for threatening his fellow 11 colleagues due to using the incident in an attempt to remove Albus Dumbledore from Hogwarts.

Discovery of Horcruxes
Four years later, In 1997, Albus Dumbledore and Harry discovered Voldemort's Horcruxes. His diary was a horcrux, as were Marvolo Gaunt's Ring, Salazar Slytherin's Locket, Helga Hufflepuff's Cup, Rowena Ravenclaw's Diadem and Nagini. Dumbledore held it secret that Harry was actually the last Horcrux.

Future openings
In 1998, During the Battle of Hogwarts, Ron Weasley and Hermione Granger opened the Chamber to take a basilisk fang to destroy the Horcrux Cup.

Deaths

 * Moaning Myrtle (1943)
 * Ginny Weasley (1993) (Nearly died) (Writing on wall said: HER SKELETON WILL LIE IN THE CHAMBER FOREVER)

Petrifications

 * Several victims (1942-1943)
 * Mrs. Norris (1992) (Writing on the wall said: THE CHAMBER OF SECRETS HAS BEEN OPENED, ENEMIES OF THE HEIR, BEWARE) (water)
 * Colin Creevey (1992) (camera)
 * Justin Finch-Fletchley (1993)
 * Nearly-Headless Nick (1993) (full face, but was already dead, so he was Petrified )
 * Hermione Granger (1993) (mirror)
 * Penelope Clearwater (1993) (mirror)

Appearances

 * Harry Potter and the Chamber of Secrets
 * Harry Potter and the Chamber of Secrets (film)
 * Harry Potter and the Chamber of Secrets (video game)
 * LEGO Harry Potter: Years 1-4
 * Harry Potter and the Half-Blood Prince