Albus Dumbledore significant person Gellert Grindelwald
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. However, this scenario would never happen, as an argument between Albus, Aberforth, and Grindelwald led to a duel that resulted in Ariana's death. For the rest of his life, Albus felt guilty, never certain whether it was his own curse or another's that had killed his sister. Grindelwald stormed back to Bagshot's home and departed to begin his own rule, leaving the country hours later. As a result of his mistakes, Albus 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 used the Disarming Charm on him.
Dumbledore had another Hallow in his keeping since the death of James Potter: the Invisibility Cloak, which he had borrowed to examine. When James died, Dumbledore kept the cloak and decided to pass it on to Harry, James' 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; Draco's soul would have been damaged in killing Dumbledore out of malice, whereas Snape was fully aware that he would be merely sparing Dumbledore pain and humiliation. He also intended for Snape to be the one to kill him and for the Elder Wand to be buried with him, in order to prevent the wand from being passed on again.
Dumbledore's spirit appears to Harry towards the end of the book in a limbo-like King's Cross, after Harry is struck with the Killing Curse which was conjured by Voldemort. During the last book, Harry finds out that he must die because he is a Horcrux. When Voldemort conjures the Killing Curse, Harry does not fight back, which stops him from dying. When they meet again, 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 and killing 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. He keeps the Cloak, leaves the Stone in the Forbidden Forest where he dropped it, and returns the Elder Wand to Dumbledore's tomb (from which Voldemort had stolen it). In the epilogue, it is revealed that Harry names his second son Albus Severus Potter after Dumbledore and Snape.Backstory
Through various interviews and discussions about the character, Rowling has established that Albus Dumbledore was born in July or August 1881 to Percival and Kendra Dumbledore. The character had previously referenced his brother Aberforth, and in Harry Potter and the Deathly Hallows, it is revealed that Albus is three years older than Aberforth. The same book introduced their sister Ariana who, at six years old, suffers a vicious attack by three male Muggle youths who had witnessed her doing magic. Frightened, they first try to get her to repeat what they had seen, and upon her failure to recreate it due to her young age, they try to stop her from being "different". The severe trauma of the attack leaves Ariana unable to function socially or to properly perform magic again. It is not explicitly stated in the novel what form this attack took, but Percival is given a life sentence in Azkaban for tracking down and hexing the boys who traumatised his daughter. To prevent her being institutionalised in St. Mungo's Hospital, or hurting someone accidentally with her uncontrolled magic, Kendra moves the family to Godric's Hollow, and conceals Ariana's illness. Their wizarding neighbours and acquaintances assumed that Ariana is a non-magical squib, and that Kendra is hiding her out of shame.
When Dumbledore and his friend Elphias Doge leave Hogwarts at the age of 18, they plan to take their "then-traditional" tour of the world. On the eve of their trip, however, Ariana accidentally kills Kendra during one of her uncontrolled outbursts of magic. Because Dumbledore's parents are absent (his father in Azkaban and his mother dead), he becomes the head of the family and it becomes his duty to put food on the table, as the family's misfortunes have left them poor. He is forced to remain in his house with Ariana while Aberforth completes his education. Aberforth knows of his brother's resentment and offers to care for Ariana himself, claiming that she prefers him to Albus, but Albus refuses, stating that it is his duty as the eldest child to care for the family.
When Gellert Grindelwald arrives at Godric's Hollow, he and Dumbledore become immediate friends, and the two dream of a new world order in which wizards rule over Muggles "for the greater good". Dumbledore and Grindelwald suggest that they have to leave the Dumbledore home to carry on their plans, but Aberforth protested against this, as Ariana's condition would not allow her to be moved. The ensuing argument between Albus, Aberforth and Grindelwald turns into a duel, and as Ariana becomes more and more stimulated, she is caught in the crossfire and killed - though neither Albus nor Aberforth are sure whether one of them or Grindlewald caused her death. Stricken with grief and remorse, Dumbledore breaks ties with Grindelwald for good. According to the author, as a result of this, Dumbledore's boggart becomes Ariana's corpse. In Philosopher's Stone, he also mentions to Harry that the deepest desire of his heart, revealed by the Mirror of Erised, is to have a pair of woollen socks, but in the seventh novel, Harry realises that he and Dumbledore see the same thing in the Mirror: their reunited families.