Albus Dumbledore
Background
Albus Percival Wulfric Brian Dumbledore is the headmaster at Hogwarts School of Witchcraft and Wizardry.
During the events of Harry Potter and the Sorcerer's Stone (2001) played by Richard Harris
Dumbledore uses his delluminator to capture the light from the streetlamps on Privet Drive. Professor McGonagall transforms from a cat and shortly after, Hagrid arrives on his flying motorcycle and hands Harry Potter to Dumbledore and he leaves a note to Aunt Petunia Dursley and Uncle Vernon Dursley. Ten years later, Dumbledore tells the first year students the rules including that the Dark Forest is off limits. The first to get sorted into their house is Hermione Granger, then Draco Malfoy, Susan Bones, Ron Weasley, and Harry. During Christmas break, Harry spends the a few nights sitting in front of the Mirror of Erised until Dumbledore catches him and warns him about the effects of the mirror. After retrieving the Sorcerer's Stone, Harry wakes up in the hospital to presents left to him by his admirers. Dumbledore tells Harry the Sorcerer's Stone has been destroyed and warns Harry that there are ways in which Voldemort may return.
During the events of Harry Potter and the Chamber of Secrets (2002) played by Richard Harris
Professor Snape threatens to kick Harry and Ron out of Hogwarts and Dumbledore and Professor McGonagall walk into Professor Snape's office and Professor McGonagall gives Harry and Ron detention. After Mrs Norris is petrified, Dumbledore and the professors walk up and Dumbledore tells the students except for Harry, Ron and Hermione to return to their rooms. Professor Snape says it is suspicious how Harry was present at the time and Gilderoy Lockhart tells him, Harry was with him. Dumbledore then mentions Professor Sprout's Mandrakes and tells Mr Filch, Mrs Norris will be fine. Later, Madam Pomfrey, Professor McGonagall and Dumbledore escort two other professors who bring Colin Creevey into the nurse's station on a stretcher in a petrified state. They take Colin's camera from his hands to look if he took a photo of his attacker, but the camera exhibits a poof of magic. Dumbledore tells Professor McGonagall the Chamber of Secrets has been opened again. Harry walks into Dumbledore's office and Fawkes erupts in flames and falls to ashes. Dumbledore tells Harry phoenixes bursts into flames when they die, but are then reborn from the ashes. Hagrid barges into the room and tells Dumbledore, Harry is not the guilty one. Dumbledore tells Harry he doesn't believe it was him that opened the Chamber of Secrets. Later, Hagrid lets Dumbledore and Cornelius Fudge come inside his hut. Cornelius tells Hagrid that he will have to take Hagrid to Azkaban due to the attacks on the students. Lucius Malfoy walks in and tells Dumbledore the governors have decide it is time for Dumbledore to step aside as Headmaster of Hogwarts. As Hagrid is leaving with Cornelius, he mentions to follow the spiders and someone will have to feed Fang. After they save Ginny Weasley, Dumbledore awards special awards to Ron and Harry and gives Ron papers to have Hagrid released from Azkaban. Harry tells Dumbledore he worries about the similarities between Tom and himself and Dumbledore tells him Voldemort transferred some of his powers to Harry when he tried to kill him. Lucius walks into the room with Dobby and is upset to see Dumbledore back at Hogwarts. Dumbledore shows Lucius the journal that was used to entrance Ginny and Dobby motions at Lucius to Harry. Before the end of the year feast, Dumbledore asks for a round of applause for Professor Sprout and Madam Pomfrey and all of the students and professors clap, including Madam Pince. Hagrid returns and everyone gives Hagrid a round of applause.
During the events of Harry Potter and the Prisoner of Azkaban (2004) played by Michael Gambon
Before their feast, Dumbledore introduces the students to Professor Lupin. Dumbledore announces that Hagrid will be teaching the Care of Magical Creatures course. Dumbledore then warns the students not to get in the way of the Dementors. Later, the Fat Lady in Painting disappears from the common room portrait. Dumbledore arrives with Mr Filch, who is holding Mrs Norris, and Dumbledore tells Mr Filch to round up the ghosts to search for the Fat Lady. Mr Filch spots the Fat Lady and she tells them Sirius Black is in the castle. At the Quidditch match, while Harry is chasing the snitch, he is attacked by Dementors and loses consciousness and begins to plummet to the ground. Dumbledore stops his fall. On the day of Buckbeak's execution, Dumbledore, Fudge and The Executioner walk to Hagrid's hut. They enter the hut and Dumbledore spends a lot of time talking and by the time they leave the hut, Buckbeak is gone. Dumbledore then tells Fudge there is no way anyone can accuse Hagrid of freeing Buckbeak due to him being with them the entire time. After Harry is found unconscious with Sirius, Dumbledore walks into the clinic and Hermione and Ron tell him that Sirius is innocent. He tells him that he believes them, but others probably wont. Dumbledore tells Hermione and Harry where Sirius is being held and gives hints to Hermione on how to save two lives. He leaves the clinic and sees Harry and Hermione and Harry and Hermione tells him they saved Sirius and Buckbeak and he acts like he doesn't know what she is talking about and leaves.
During the events of Harry Potter and the Goblet of Fire (2005) played by Michael Gambon
As Dumbledore is talking to the students, Mr Filch runs up and tells him something. Dumbledore continues and tells the students that Hogwarts will be hosting the Triwizard Tournament. Dumbledore introduces Madame Olympe Maxime and the students of the Beauxbatons Academy of Magic, including Fleur Delacour. He then introduces Igor Karkaroff and the students of Durmstrang, which includes Viktor Krum. Dumbledore introduces Maxime to Hagrid. The Goblet of Fire is brought into the hall and Dumbledore tells the students that whoever wins the tournament will have eternal glory. Alastor "Mad-Eye" Moody walks into the hall and is greeted by Dumbledore. Barty Crouch tells the students that no student under the age of 17 will be able to apply to participate for the Triwizard Tournament. During the champion selection, Cedric Diggory, Viktor, Fleur and Harry's names are chosen. Maxime and Karkaroff accuse Harry of cheating, but Barty Crouch says Harry must compete. McGonagall tells Dumbledore he can't allow Harry to compete, but Snape thinks they should allow Harry to compete until they figure out what is going on.
Harry goes to Dumbledore's office to speak to him and Dumbledore leaves temporarily to see Cornelius Fudge out. Harry tells Dumbledore about the dream he had and how he saw Barty Crouch Junior in the dream. The final challenge begins and the challengers enter a maze. Harry is transferred back to the maze location and Dumbledore notices something is wrong. Harry yells that Voldemort is back and Moody pulls Harry away while Amos Diggory cries over Cedric's body. Moody starts to transform and as he is about to kill Harry, Dumbledore bursts into the room and stuns Moody with magic. Snape pours a potion into Moody's mouth. Dumbledore, Snape and McGonagall find the real Moody locked in a chest and the fake Moody fully transforms back to Barty Crouch Junior. Later, Dumbledore gives a eulogy for Cedric and tells the students that Voldemort murdered him.
During the events of Harry Potter and the Order of the Phoenix (2007) played by Michael Gambon
During the Hogwarts banquet, Dumbledore welcomes back Professor Grubbly-Plank as the Care of Magical Creatures while Hagrid is away. He then introduces Dolores Umbridge as the new Defense Against the Dark Arts teacher. Dolores interrupts Dumbledore and tells the students that the Ministry of Magic is very concerned about their education. Dolores and McGonagall have an argument about Harry's punishment and Dolores declares that things at Hogwarts are worse than the Ministry thought. Filch posts a decree stating that Dolores has been appointed as the Hogwarts High Inquisitor. Professor Sybil Trelawney is fired by Dolores and Dolores has Filch bring Trelawney's things out to the courtyard. Dumbledore walks out into the courtyard and has McGonagall bring Trelawney's things back inside and tells Dolores she can only fire professors, not expel them from Hogwarts.
Harry has a nightmare that Mr Weasley was attacked by Nagini and tells McGonagall who takes him and the Weasley children to Dumbledore. Harry tells Dumbledore about his dream and Dumbledore tells Everard to contact those at the Ministry to save Mr Weasley and has Phineas notify the Order of the Phoenix. Percy Weasley drags Harry and Cho Chang, to the meeting with Fudge, Kingsley Shacklebolt, Dawlish and Dolores in Dumbledore's office. They accuse Dumbledore of forming an army to revolt against the Ministry. Fudge orders Kingsley and Dawlish to take Dumbledore to Azkaban and Dumbledore escapes with the help of Fawkes. As the battle at the Department of Mysteries rages, Fudge and other members of the Ministry appear and when Voldemort is ultimately defeated by Dumbledore and runs away, Fudge finally acknowledges that Voldemort is back. The Daily Prophet reports that Harry has been vindicated, Dumbledore has been reinstated and Dolores has been suspended.
During the events of Harry Potter and the Half-Blood Prince (2009) played by Michael Gambon
Harry and Dumbledore are standing in the Ministry directly after Dumbledore's battle with Voldemort. Back in London, Harry thinks he sees something and looks out the cafe window and Dumbledore appears outside across the subway tracks. Harry walks over to Dumbledore and sees one of Dumbledore's hands has started to turn black. Harry looks across and sees the Waitress leaving work and looking for him, but Dumbledore forces him to come with him. They Apparate to Budleigh Babberton and go inside a nearby house. They find the house in disarray and Professor Horace Slughorn disguised as an armchair. Dumbledore introduces Harry to Slughorn and Slughorn tells them that the Death Eaters have been trying to recruit him and so he has been constantly moving from home to home. Slughorn then agrees to become a teacher at Hogwarts.
Dumbledore tells Harry that he won't be returning home and Dumbledore Apparates Harry to the Weasley home. Harry and Luna Lovegood walk into the banquet hall and Dumbledore introduces the students to Slughorn and tells the students that dark forces are trying to penetrate Hogwarts. Harry goes to Dumbledore's office and Dumbledore shows him the memory of the first time Dumbledore met Voldemort. In the past, Dumbledore goes to Wool's Orphanage and is met by Mrs Cole who takes him to meet an 11 year old Tom Riddle. Dumbledore then invites Tom to come to Hogwarts. After the memory ends, Dumbledore tells Harry that Tom became close with Slughorn. During the school year, Harry watches another memory, this time of Voldemort at one of Slughorn's dinner parties. After the dinner party, Voldemort asks Slughorn about dark magic and Slughorn tells him he won't tell him about them. Dumbledore tells Harry that Slughorn tampered with the memory and asks Harry to find out what he changed. After he cures Ron of being lovesick, Slughorn pours a drink for Ron, Harry and himself and after Ron drinks it, he starts to convulse. Harry gives Ron a bezoar and at the hospital, Ron is taken care of by Madame Pomfrey. Slughorn tells Dumbledore that he initially intended on giving him the liquor as a gift. While in bed Ron calls for Hermione in his sleep in front of Lavender Brown.
Slughorn gives Harry his untampered memory and Harry brings it to Dumbledore. They watch the memory and see that Slughorn told Voldemort about Horcrux magic. Dumbledore pulls out a ring and Voldemort's diary, which he identifies as Horcrux which have been destroyed. They travel to a large cave and take a boat to the location of another Horcrux. Dumbledore starts drinking from a small pool of water that causes him pain. After he drinks all the water, Harry finds a locket in the bottom of the pool. As Harry is getting Dumbledore cave water, an Inferi grabs his arm and Harry and Dumbledore have to battle their way out of the cave crawling with Male Inferi and Female Inferi. Harry and Dumbledore return to Hogwarts and Dumbledore tells Harry to get Snape. They hear a door open and Dumbledore tells Harry to hide. Draco walks up to Dumbledore and shows him his Death Eater tattoo and tells Dumbledore that he was chosen by Voldemort to kill him. Draco casts Expelliarmus on Dumbledore, disarming him. Bellatrix, Fenrir Greyback, Amycus, Alecto, and Rowle walk over to Draco and Snape sneaks up on Harry. Snape goes to where the others are and casts Avada Kedavra on Dumbledore, killing him.