Albus Dumbledore

In the opening chapter of the first novel of the series, Harry Potter and the Philosopher's Stone, Dumbledore arrives at number four, Privet Drive in Little Whinging, Surrey. When Harry's parents were killed and Voldemort was rendered to a feeble form, it was Dumbledore's decision to place the now-orphaned Harry in the home of Vernon and Petunia Dursley. He knew that Harry would be protected by the special magic caused by his mother's sacrifice, after he evoked the magic of the bond of blood and Petunia Dursley sealed it by accepting Harry into her home. This old magic of binding love made touching Harry unbearable for Voldemort. Dumbledore left Harry upon the doorstep of the Dursley residence with a letter explaining the situation. He departs with the final phrase, "Good luck, Harry."

When Harry arrives at Hogwarts, Dumbledore tells Harry about the secrets of the Mirror of Erised, claiming that when he looks into it, he sees himself "holding a pair of thick, woollen socks." However, he, like Harry, sees his family alive and united. He also is responsible for somehow enchanting the Mirror so that it hides the Philosopher's Stone and only someone who looked into the Mirror and whose desire was "to find the Stone...but not use it" would actually receive it. He is called out to the Ministry of Magic by a false message on the night when Professor Quirinus Quirrell, Harry, Ron Weasley, and Hermione Granger enter the dungeons to retrieve the Stone, but realises during the trip that he is needed at Hogwarts and returns in time to rescue Harry from Quirrell and Voldemort. He also has a final conversation with Harry after the events down in the dungeons and tells him that he is too young to comprehend the information about why Voldemort attempts to kill him.

In Harry Potter and the Chamber of Secrets, Dumbledore suspects that Tom Riddle is somehow involved in the attacks on the students, as he says, when asked who is the culprit, "not who, but how?” A younger Dumbledore appears in Riddle's diary, when Harry sees his memory, and asks Riddle if he knows anything about the attacks on the students. During the last half of the novel, Lucius Malfoy coerces the school's other eleven governors to suspend Dumbledore as Headmaster in the wake of attacks by a basilisk in the school when the Chamber of Secrets is opened. Dumbledore is reinstated when the governors discover that Ginny Weasley was taken into the Chamber of Secrets and Lucius is found to have coerced the other governors into suspending him.

At the beginning of Harry Potter and the Prisoner of Azkaban, Dumbledore is forced to accept Dementors onto his school's grounds for the protection of his students from Sirius Black, the supposed killer that had escaped from Azkaban. After Black's breach into Hogwarts, Dumbledore issues orders to close every entrance to the school and grounds. After Harry falls off his broomstick during a Quidditch match because of the Dementors, Dumbledore becomes uncharacteristically angry with them and uses his wand to cause Harry to levitate safely to the ground. Later in that book, Dumbledore suggests Hermione Granger use her Ministry-approved Time-Turner to go back three hours to save Buckbeak the hippogriff and Sirius from their unjust executions.
In the fourth instalment, Harry Potter and the Goblet of Fire, Dumbledore introduces the Triwizard Tournament. He also serves as a judge during the entire event. When Harry's name comes out of the Goblet of Fire, Dumbledore is not enraged but remains calm, simply asking Harry whether he had himself, or had asked an older student, to submit his name. When Harry answers no, he believes him. By the end of the book, Dumbledore's fears are realized when Harry returns from his encounter with Voldemort clutching the dead body of Cedric Diggory and when Alastor Moody (actually being impersonated by Barty Crouch Junior through Polyjuice Potion) takes Harry away from Dumbledore and to his office inside the castle. Dumbledore immediately becomes suspicious and heads straight towards Moody's office with Minerva McGonagall and Severus Snape to save Harry and to interrogate Crouch. Afterwards, Dumbledore listens to Harry's eyewitness account about Voldemort's return. Harry though only wakes up later to find Minister for Magic Cornelius Fudge in the wing arguing with McGonagall and Dumbledore, the latter of whom enters into an argument with Fudge. In the end, Fudge and Dumbledore "part ways" after an argument about the situation of Voldemort's return and the consequences that would follow should Fudge remain ignorant.

In Harry Potter and the Order of the Phoenix, Dumbledore is demoted from Chief Warlock of the Wizengamot, voted out of the Chairmanship of the International Confederation of Wizards, and is almost stripped of his Order of Merlin First Class, due to his speeches regarding the return of Voldemort. Meanwhile, the Ministry of Magic does everything they can to discredit him and Harry, mainly through the Daily Prophet. At the beginning of the book, Dumbledore enrages Fudge when he stops by at Harry's hearing with a witness (Arabella Figg) to ensure that he is not expelled. While Harry feels better when Dumbledore assists him, he becomes annoyed to the point of being angry that the headmaster refuses to speak or even look at him.

During the following year at Hogwarts, the Ministry passes Educational Decree Twenty-two, allowing Fudge to place Dolores Umbridge (after Dumbledore failed to find a suitable candidate) to the post of Defence Against the Dark Arts teacher. Through her, Fudge gradually gains power over Hogwarts and Dumbledore, who he fears is building an underage wizard army to overthrow the Ministry. Umbridge forbids practical defense practice in her classes, forcing Harry, Ron, and Hermione to form Dumbledore's Army with fellow friends. It is when the Ministry discovers the D.A. that Dumbledore, choosing to accept the responsibility, falsely claims that the organisation was his own subversive creation, and allows himself to be removed as headmaster (for the second time) rather than allow Harry to be expelled.

Dumbledore is not heard of again in the book until he arrives in the Department of Mysteries to aid the Order in the battle against the Death Eaters. He subdues all of the Death Eaters, except for Bellatrix Lestrange, and binds them with an Anti-Disapparition Jinx to prevent them from magically escaping. He then saves Harry from the Avada Kedavra curse conjured by Voldemort and proceeds to engage in a ferocious duel with the Dark Lord, which ends in a virtual stalemate. After Voldemort disapparates, Dumbledore tells Fudge what happened and is reinstated as headmaster and retrieves all his distinctions. Towards the end of the book, Dumbledore explains to Harry that Voldemort chose him as his equal and that one must kill the other in the end.
In Harry Potter and the Half-Blood Prince, Dumbledore fetches Harry from Privet Drive and takes him to persuade Horace Slughorn to join the Hogwarts staff; his right hand, Harry notices, is shrivelled and black. During the school year, Dumbledore meets with Harry in his office to teach him of Voldemort's past because he tells Harry that it is of immense importance. Through their lessons, they visit the thoughts of others, which contained important information about the life of Voldemort, leading to his genocidal rise to power. It is learned that Voldemort created six Horcruxes to gain immortality and that they must all be destroyed before Harry goes after the final piece of Voldemort's soul that resides in the Dark Lord's body. Harry also repeatedly warns Dumbledore in most of their lessons that another student, Draco Malfoy, is working for Voldemort. Dumbledore refuses to take any action against Draco, and instead tells Harry that he already knows more about what is happening than Harry does.

By the end of the book, Dumbledore and Harry set out to the cave where Dumbledore believes a Horcrux resides. In the cave, Dumbledore drinks a potion inside the Horcrux's container; while drinking it, he begins to scream, seemingly enduring mental torture and being weakened. Dumbledore begins to scream out for water after he finishes the potion, and Harry, realizing he has no other choice, dips the goblet into the lake to give him a drink. As soon as he does this, though, all the Inferi that reside in the lake grab at Harry and attempt to drag him down and drown him in the lake. But Dumbledore suddenly recovers, thanks to the water, and conjures a fire lasso around them. Dumbledore takes the locket within and both make their way back out of the cave and back to Hogsmeade. When they return, Madam Rosmerta informs them that the Dark Mark was conjured over the Astronomy Tower and both Harry and Dumbledore set off on Rosmerta's brooms towards the tower. In the tower, Dumbledore puts Harry into a body-binding curse under his invisibility cloak and merely converses with Draco about the plot to kill him. Several other Death Eaters enter the tower and try to persuade Draco to kill Dumbledore. When Malfoy is unable to murder him, Snape appears and immediately performs the Killing Curse on Dumbledore.

Shortly after his death, Dumbledore's portrait magically appears in the Headmaster's office. His funeral is attended by students, Hogwarts teachers and staff, members of the Ministry of Magic, ghosts, centaurs, merpeople and others who wish to pay their respects. Shrouded in purple velvet, he is entombed in a white marble sarcophagus beside the lake at Hogwarts, and it is said that he is the only headmaster to be buried on the school grounds.
Rowling used several chapters in Harry Potter and the Deathly Hallows to reveal two main matters concerning Dumbledore: his early life and his death. The book introduces Albus's parents, Percival and Kendra Dumbledore, as well as his little sister, Ariana; his brother, Aberforth Dumbledore, was mentioned in previous books. At six years old, Ariana suffered a vicious attack by three Muggle boys who had witnessed her doing magic. Because of this attack, Ariana was seriously traumatized and never able to control her magic again, having recurring outbursts of magic. Percival cursed the Muggle boys in revenge, and was sentenced to life in Azkaban. After this, Kendra moved her family to the village of Godric's Hollow. However, in one of her outbursts, Ariana accidentally killed Kendra just as Albus completed his education. Because Dumbledore's parents were absent, Albus became the head of the family and was forced to remain in his house with his sister Ariana while Aberforth completed his education.

Soon afterward, a young Gellert Grindelwald arrived in Godric's Hollow to live with his great-aunt, Bathilda Bagshot, author of A History of Magic. The two young men took to each other immediately, and together they dreamed of a world ruled by wizards over Muggles by uniting the legendary Deathly Hallows. They believed that if they were forced to destroy a few along the way, it would still be "for the greater good", and the sufferings and losses would be rewarded a hundredfold in the end. This scenario would never happen, though. A discussion between Albus, Aberforth, and Grindelwald led to a duel that resulted in Ariana's death. For the rest of his life, Dumbledore felt guilty, never certain whether it was his own curse or another's that had actually killed his sister. Grindelwald stormed back to Bagshot's home and departed to begin his own rule. As a result of his mistakes, Dumbledore felt that he was not to be trusted with power and, because of this, never took the position of Minister for Magic, despite being offered it several times. Dumbledore returned to Hogwarts as professor of Transfiguration, and he served in recruiting students for the school.

Decades later, in 1945, Dumbledore finally defeated the now-Dark wizard Grindelwald, who had come to possess the Elder Wand. Grindelwald's defeat made Dumbledore the master of the Elder Wand, which remained his until just before his death, when Draco disarmed him. Dumbledore was temporarily in possession of another hallow when, before the murders of the Potters, he asked James to let him see the Invisibility Cloak, suspecting it to be part of the legendary Deathly Hallows. When James died, Dumbledore kept the cloak and decided to pass it on to Harry, James's son.

The truth about Dumbledore's death is revealed through Snape's last memories in the Pensieve. Harry learns that Dumbledore made a terrible error by placing a cursed ring on his right hand, sometime between the fifth and sixth book, forgetting the curses that must be on the ring. The ring held the Resurrection Stone, which Dumbledore hoped to use to allow him to apologise to his sister and parents. Dumbledore called Snape to help him; however, when Snape arrived and assessed the curse, all he could do was contain it. Snape told Dumbledore that he had little more than a year to live. After hearing this news, Dumbledore revealed to Snape that he knew about Voldemort's plan to have Draco kill him. He asked Snape to use the killing curse on him when the time came because he did not want Draco to have to kill him, saying that the boy's soul was still intact, whereas Snape was fully aware that he would be merely sparing Dumbledore pain and humiliation.

Dumbledore appears one last time to Harry towards the end of the book in a limbo-like King's Cross, after Harry is struck with the killing curse. The boy comforts Dumbledore as he confesses all of his many regrets. Dumbledore then informs Harry of the choice he still has; of moving on to the next life or returning to his body to face Voldemort one last time. After returning from the mystical King's Cross and defeating Voldemort, Harry has a short conversation with Dumbledore's portrait in the Headmaster's office about the fate of each of the three Deathly Hallows. In the epilogue, it is revealed that Harry names his second son Albus Severus Potter after Dumbledore and Snape.