Tom Marvolo Riddle (b. December 31, 1928) is a Half-Blood wizard and widely agreed to be the darkest wizard in history. He styled himself as "Lord Voldemort" and wreaked havoc on the world for over thirty years before his defeat in Godric's Hollow due to the magical protections created by Lily Potter when saving her son Harry's life. Voldemort survived this encounter thanks to the Horcruxes that he created, but he was left without a body and his powers were greatly diminished.
Tom Marvolo Riddle was born on December 31, 1928, to Merope Gaunt mere hours before her death. She had been weak and malnourished for most of her pregnancy, and she delivered him at Wool's Orphanage. Merope only had time to name him after his own father and hers before succumbing to her injuries from childbirth. As a result, Tom was raised at Wool's Orphanage for most of his early life.
Wool's Orphanage was very poor, and Tom rarely received any sort of love or affection from the staff. This resulted in him being quite cold and aggressive with the other children from an early age. He showed signs of magic early and soon began using it to torture the children that upset or bullied him, often traumatizing them for the rest of their lives. He also had a tendency to collect trophies from those that he hurt, symbols and momentos of his cruelty.
When Tom was eleven years old, Albus Dumbledore visited him to inform him about his magic and offered him a place at Hogwarts School of Witchcraft and Wizardry. In his joy over discovering his magical ability, Tom inadvertently let slip to Professor Dumbledore that he sometimes hurt other students; off-putting the man. During his trip to Diagon Alley with his new professor, Tom was unable to rectify this error.
Tom Riddle attended Hogwarts between 1940 and 1948 and he was almost immediately sorted into Slytherin house. Due to his skills as a parselmouth, Riddle quickly established himself as a leader in Slytherin--as the skill was something that Salazar Slytherin had been famous for. It was through this esteem from his peers that Riddle began to accumulate followers that would later become his loyal Death Eaters.
Academically, Riddle excelled in all of his classes. Many asserted that he was the most gifted student that Hogwarts had ever seen. He was invited by Horace Slughorn to join his group of students known as the Slug Club, and he garnered attention from all the other staff members thanks to his immense skill at magic. He proved capable of charming any of the teachers which he spoke too into helping him with whatever he wanted. The only exception to this was the Transfiguration Professor, Albus Dumbledore, who had already begun to mistrust Riddle as a result of their initial meeting.
Despite outward appearances, Riddle had not been a model student. Chaos and cruelty plagued his years at Hogwarts as he and his followers routinely attacked and injured other students. Though he was never implicated in these attacks, the students in question always too terrified to come forward, Dumbledore was both aware and watchful of Riddle during these years.
The most severe incident occurred during 1944 when Riddle opened the Chamber of Secrets and loosed the basilisk inside onto the school. Over the course of three months, beginning in November of that year, five muggle-born students were killed and seven others were petrified by the monster inside the chamber. Due to these deaths, muggle-born students had been sent home to their families, ostensibly for their protection. However, after the sixth death, a half-blood girl named Myrtle Warren, the Board of Governors of Hogwarts resolved to close the school. To prevent this, Riddle framed fellow student Rubeus Hagrid for opening the Chamber. Though the evidence against the man was circumstantial, then headmaster Armando Dipper--a pure-blood supremacist--was happy to blame the half-giant and expel him from the school. However, due to the circumstantial nature of the evidence, and with Dumbledore's prodding, Riddle failed to have the half-giant arrested or evicted from the grounds.
Riddle knew it was unsafe to open the Chamber of Secrets again while still a student, and therefore he created the first of his Horcruxes--a diary--for the purpose of reopening the Chamber at a later date and killing all muggle-borns as Hogwarts.
Upon graduation, Riddle immediately applied for the Defense Against the Dark Arts position at Hogwarts. Dippet, though fond of Riddle, denied his request because he felt that Tom was too young and too close to many of the students at the school to be a professor. For that reason, he left the school.
Rather than going to the Ministry, as many expected, Riddle took a job as a store clerk at Borgin and Burke's. It was far below what he was qualified to do, but, like with everything else, Riddle excelled at it. His true purpose, of course, was to locate valuable magical relics to steal for himself. Also, being in Knockturn Alley, he was able to learn more about the Dark Arts than he would have anywhere else in polite wizarding society. In particular, he stole Salazar Slytherin's Locket and Helga Hufflepuff's Cup from Hepzibah Smith to turn into Horcruxes before resigning from the position.
After his time at Borgin and Burke's, Riddle adopts the moniker Voldemort and begins studying darker and more advanced forms of magic. One of the first things he did was find a mage to perform a complex empowerment ritual for him to increase his magical power. For most, this would have signalled the beginning of mage training, but Voldemort felt himself above his trainer and murdered him after the completion of the ritual. He began studying and inventing dark magicks that had never been seen before in an attempt to reach immortality.
During this time, Voldemort also began amassing followers across the world. While some were from his school days, he did not stop there. He gathered dark witches and wizards to his cause from across the world and drew dark creatures to him en masse to further strengthen his army. His early followers, those whom he gathered while at Hogwarts, became his lieutenants.
Given the amount of recruitment and danger he was causing, it was only natural that the world large would take notice. Though they were unaware of who was behind the curtain, they knew that someone was gathering followers, and amassing power. The crackdowns that were then enacted on sever species were exactly what Voldemort wanted and drew even more people to him.
In 1957, the position of Defense Against the Dark Arts professor opened at Hogwarts School again and Voldemort applied. Though he no doubt suspected that he would not get it, he chose to speak to Dumbledore on the off-chance he would be appointed. He also wanted to reenter the school in order to hide one of his Horcruxes inside. He was correct; Dumbledore would not hire him. Though this was suspected, Dumbledore's utter disregard for him, and his clear insight into Voldemort's character enraged him. He then cursed the Defense Against the Dark Arts post to prevent anyone from holding it for more than one year. This, he felt, was an adequate revenge against Dumbledore and would lower the quality of education as time went on. He was, however, successful in hiding one of his Horcruxes within the school.