Lord Voldemort

Lord Voldemort, real name Tom Marvolo Riddle, is the main antagonist of the Harry Potter franchise. He is the Dark Lord, the founder and supreme leader of the Death Eaters, and the archenemy of Harry Potter. He is obsessed with ridding the wizarding world of Muggles, and aims to conquer both the wizarding world and the Muggle world alike. He is the main antagonist of Harry Potter and the Philosopher's Stone and it's film adaptation, one of the two main antagonists (alongside Lucius Malfoy) of Harry Potter and the Chamber of Secrets and it's film adaptation, the secondary antagonist of Harry Potter and the Goblet of Fire and it's film adaptation, one of the two main antagonists of Harry Potter and the Order of the Phoenix and it's film adaptation, and the main antagonist of Harry Potter and the Deathly Hallows and it's separate two-part film adaptations (the overarching antagonist of Harry Potter and the Deathly Hallows Part 1 and the main antagonist of Harry Potter and the Deathly Hallows Part 2).

Origins
Tom was born in 1928 in a London orphanage, the child of Merope Gaunt, a witch, and Tom Riddle, a Muggle. Upon discovering that Merope was a witch, Tom abandoned her. Merope died giving birth to the child, and lived just long enough to name him Tom Marvolo Riddle. With no parents to raise him, Tom was brought up in an orphanage, where he used his magical inheritage to hurt people he didn't like, and controlled the other orphans through fear.

When Tom was eleven years old, Albus Dumbledore invited him to attend Hogwarts as a student. Though he excelled as a student, Tom became obsessed with his Slytherin heritage and how to cheat death. One day, he enetred the Chamber of Secrets and released a basilisk, resulting in the death of another student, Myrtle. Tom later framed another student, Rubeus Hagrid, for the incident. At the same time, Tom renounced his born name, and instead began to go by a new name, "Lord Voldemort", seeking to one day become the most powerful sorcerer in the world.

The summer after Myrte's death, Voldemort visited his uncle, where he learned of the circumstances of his birth. In revenge for his father's abandonment, Voldemort murdered his father and grandparents. He then began to study the use of Horcruxes, creating his first two with the deaths of Myrtle and his father.

Transformation into the Dark Lord
After leaving Hogwarts, Voldemort opened up a dark magic shop named Borgin and Burkes. However, he abandoned his shop after murdering Hepzibad Smith for a gold locket that belonged to Slytherin and a gold cup. He then vanished for years, during which he began to practice the dark arts and consorted with evil witches and wizards. He eventually arose to become the Dark Lord Voldemort, amassing a legion of witches, wizards and other dark creatures. Voldemort's followers would become known as Death Eaters. Each Death Eater bore a sign, the Dark Mark, burned into their skin by Voldemort.

For over a decade, Voldemort unleashed a reign of terror, wiping out those who opposed him and defended the rights of Muggles, who Voldemort regarded as inferior. To counteract Voldemort's army, Dumbledore organized a resistance called the Order of the Phoenix. However, the Order was outnumbered, and Voldemort's army began to kill off members of the resistance, along with their families.

Voldemort's reign of terror would come to an end, however, when he was betrayed by two of his followers, Severus Snape and Regulus Black. Regulus died trying to sabotage one of Voldemort's Horcruxes, and Severus secretly allied himself with Dumbledore after Voldemort decided to kill the Potter family to avert a prophecy that proclaimed that a child would be born who could defeat him. Voldemort attempted to kill the child, named Harry, and though he managed to kill the infant's parents, he was defeated when one of his curses rebounded on him, destroying his physical form.

With Voldemort's defeat, the Death Eaters were captured, with many being sentenced to Azkaban for their crimes. However, Voldemort hadn't been permanently defeated, as his Horcruxes proved successful in allowing his spirit to remain. However, for nearly a decade, he could only survive by possessing the bodies of others.

Second defeat
In 1992, Voldemort possessed Hogwarts professor Quirinus Quirrel while he was visiting Albania. Arriving in England, Voldemort attempted to acquire Flamel's Philosopher's Stone to increase his strength, but it was hidden by Dumbledore. While attempting to retrieve the stone, Voldemort met Harry in front of the Mirror of Erised, where he attempted to kill the boy. However, as a result of a protection spell cast by Harry's mother Lily, Voldemort could not physically touch Harry without intense pain. Voldemort abandoned Quirrel to die, and Harry and Dumbedore destroyed the stone. Defeated, Voldemort returned to his forest in Albania.

Rebirth
Voldemort developed a plan to regenerate his physical body, acquiring two followers: Peter Pettigrew and his pet snake Nagini. With Peter's help, Voldemort conjured a temporary potion to create a rudimentary body. However, full regeneration recquired the bone from his father, the the flesh of a servant, and the blood of a foe. Voldemort, seeking revenge on Harry for destroying his physical form, chose his blood to extract.

Voldemort and Peter tortured an informant named Bertha Jorkins for information, then killed her. He then hatched a plan with Barty Crouch, Jr. to bring Harry to the Little Hangleton graveyard for Voldemort's rebirth. This plan succeeded, and Harry and the "spare", Cedric Diggory were taken to the graveyard. Cedric was killed, and the resulting potion allowed Voldemort to gain physical form once more, with Lily's protection spell being broken as well.

With his physical form made manifest once more, Voldemort called upon the surviving Death Eaters to come to him and re-pledge their allegiance to him. He then duelled Harry, but as their wands both shared the same core, neither could defeat the other. Voldemort's victims then appeared in spectral form, and Harry's parents helped him escape Voldemort's clutches.

Second Wizarding War
Voldemort made several attempts to retrieve the records of the prophecy foretold by Serverus Snape, stored in the Department of Mysteries, but all of these attempts failed. Eventually, he tricked Harry into entering the Department of Mysteries, planning for his Death Eaters to snatch the records once he found it. However, this plan failed as well, and the prophecy was destroyed in battle. As his Death Eaters were overwhelmed by the Order of the Phoenix, Voldemort appeared and attacked Harry directly, managing to possess his body. However, Harry's loving heart proved inimical to Voldemort, who was forced out of his body.

Voldemort, seeking Dumbledore's death, recruited the teenage Draco Malfoy to murder him and gather a group of Death Eaters to take over Hogwarts. Though Draco was ultimately unable to fulfill Voldemort's orders, Dumbledore was ultimately killed by Severus Snape. Prior his death, however, Dumbledore shared the knowledge of the Horcruxes with Harry.

Voldemort, after freeing Lucius and the other Death Eaters from Azkaban, organized a silent coup that led to him seizing control over the Ministry. He then unleashed another reign of terror against the Muggles and Muggle-born wizards, with mass killings being rampant. During this time, Voldemort also sought out a wand that would be effective against Harry. Learning of an invincible wand known as the Elder Wand, the most powerful wand known to man, Voldemort set out to find it. He eventually located the wand in the tomb of Dumbledore.

The Battle of Hogwarts
Upon learning that Harry and his friends were destroying his Horcruxes, Voldemort gathered an army of Death Eaters to attack Hogwarts. Prior to the battle, Voldemort gives the students and teachers of Hogwarts the chance to give Harry up, but they refuse. When the deadline passes, Voldemort unleashes his army of Death Eaters on the school.

During the battle, Voldemort murdered Severus Snape, believing that it would give him a stronger connection to the Elder Wand. Before his death, Snape passed his memories to Harry, who then discovered that Dumbledore was actually dying and that his was planned by him and Snape, who was reluctant to do so. Harry also discovers that he contained the seventh Horcrux and had to sacrifice his life for Voldemort to be stopped. He surrenders himself to Voldemort, who hits him with the Killing Curse. However, this fails to kill Harry and only destroys the Horcrux. Instead, he was sent to a limbo of Kings Cross Station, where he witnessed the remains of Voldemort's soul, and made the choice to return to the battle to finish Voldemort off once and for all.

As the battle commenced, Nagini was decapitated and Bellatrix Lestrange was killed by Molly Weasly, enraging Voldemort, who tried to kill her. However, Harry returned and continued his battle with Voldemort. During their duel, Harry revealed that Snape was not the true master of the Elder Wand; it was Draco, and since Harry had defeated Draco, that made him the true master. Voldemort, refusing to believe Harry, casts the Killing Curse on him. However, Harry was indeed the true master, and the spell rebounded upon Voldemort, killing him once and for all.

After his death, Voldemort's soul, damaged by the Horcruxes, was unable to pass on into the afterlife or return as a ghost, and is cursed to remain in limbo for all of eternity.