Second skirmish at the Cave

The second skirmish at the Horcrux cave took place in June 1997 after Albus Dumbledore tracked down what he believed to be one of Lord Voldemort's Horcruxes, located in a seaside cave Tom Riddle had visited as a boy while living in Wool's Orphanage.

Tom Riddle's childhood
As a child, Tom Riddle and some other children were taken by his orphanage to a place nearby the cave for an outing. He took two children, Dennis Bishop and Amy Benson to the cave and terrorised them to the point that the two children were unable to speak of what happened. It is likely he magicked their way down to the cave scaring the other children in the process.

Plot to kill Albus Dumbledore
Over time Albus Dumbledore came to suspect Voldemort had created Horcruxes. In 1993, he received proof of his theory when Harry Potter described the way in which Tom Riddle's Diary, which was subsequently turned over to him, acted and set off to find and destroy them all. When he found Marvolo Gaunt's Ring in the Gaunt Shack, he realised that one of the Deathly Hallows, the Resurrection Stone, was set in it, and temporarily forgot that the ring was a horcrux. He placed it on his finger hoping to see his sister, father, and mother in order to ask forgiveness for the mistakes of his youth. His hand was cursed horribly, but thanks to his own prodigious skill and Severus Snape's good timing, the curse was stopped for the time being. Dumbledore knew that he would eventually die, and he and Snape set up a plan for Snape to kill Dumbledore. This would accomplish several ends: not harming the soul of Draco Malfoy, whom he assumed Voldemort was using to punish the Malfoy family by ordering Draco to kill him, and cancelling the powers of the Elder Wand.

Draco Malfoy's mother and aunt, however, went to see Snape in his home. Narcissa was horribly upset by the task Draco was ordered to do. Bellatrix thought otherwise, saying that her sister should be honoured Draco was given such a task. Snape made Narcissa an Unbreakable Vow, promising that he would help Draco whenever needed, and that if Draco should not succeed, Snape would fulfill the task himself.

Draco thought that if he could fix the Vanishing Cabinet in the Room of Requirement, he could bring Death Eaters into the school. It took him most of the year to do so, and at times he was worried that it would not work. As such, he put Madam Rosmerta under the Imperius Curse. He made her give Katie Bell a cursed Opal necklace, cursing Katie and not getting anywhere close to Dumbledore, and poison mead, for Horace Slughorn to give Dumbledore for a Christmas present. This too did not reach Dumbledore, instead it was consumed by Ron Weasley who would have died if it was not for the quick work of his friend Harry Potter.

Harry and Dumbledore's lessons
Knowing that he had little time left, Dumbledore began giving Harry Potter private lessons in Harry's sixth year. The object of which was to teach him about Voldemort, his past, his Horcruxes, and his way of thinking, so that once Dumbledore inevitably died, Harry would be able to continue the hunt for Horcruxes and destroy them all. They began the first Saturday after the new term started at Hogwarts. In their first lesson, Harry and Dumbledore viewed Bob Ogden's memory by use of the Pensieve. From this memory, Harry learned of the family roots of Tom Riddle, the Gaunt family on the magical side and Tom Riddle Sr. on the Muggle side. He also learned of the final two heirlooms of the long impoverished Gaunt family, Salazar Slytherin's Locket and Marvolo Gaunt's Ring, the mental instability of Riddle's magical family, and Merope Gaunt's use of a Love Potion to ensnare Tom Riddle Sr.



On a Monday a little over a month later, Harry and Dumbledore had their second lesson. This time they ventured into one of Dumbledore's own memories. While watching the boy, Tom Riddle, as he learned he was a wizard, they gleaned many pieces of information including, his thoughts of death as being a human weakness, his like for gathering trophies, his dislike of having a common name, his enjoyment of solitude and his preference for acting alone most likely stemming from being raised in an orphanage, and his measure of control and intent when using his magic. They discussed the end of Merope Gaunt's life in London and the pawning of the Locket. After the Christmas holidays, the lessons resumed. In their third lesson, Harry and Dumbledore witnessed Tom Riddle discover his heritage and blood status. After the brief memory, they speculated on what happened and came to the same conclusions. Tom Riddle stunned his uncle, stole his wand and used it to murder his muggle relations, the Riddle family. He then replaced the wand, implanted false memories in Morfin Gaunt, and stole Marvolo Gaunt's Ring from him. They also watched the falsified memory of Horace Slughorn, and Harry was assigned to obtain the real one. Before he left, Harry and Dumbledore also talked about Riddle's "friends" which reinforced their idea that he was a loner.

By Mid-March Harry had yet to obtain the real memory from Professor Slughorn, for which he was chided by Dumbledore at the outset of their fourth meeting. In another odd memory, Harry and Dumbledore visited the home of Hepzibah Smith. There, they watched as Tom Riddle, the poor assistant from Borgin and Burkes, learned of the existence of Helga Hufflepuff's Cup and Salazar Slytherin's Locket. They discussed her mysterious death just days later, making the assumption that Riddle stole the two valuable items. They also watched another of Dumbledore's memories, in which Voldemort came to ask for the Defence Against the Dark Arts professorship. They discussed the possibility that Voldemort wanted to search the castle. A few weeks later, Harry obtained the memory under the influence of Felix Felicis. Late that night, he and Dumbledore delve into the memory. They discover that Lord Voldemort planned on making seven Horcruxes and that he most likely made them with those priceless items he had stolen. They discussed how big a job remained for them, and Dumbledore promised Harry that he could accompany him if he were to find another.

Finding the Fake Locket Horcrux
One evening in June 1997, Harry Potter was summoned to Dumbledore's office. Thinking that he must have found a Horcrux, Harry hastened to the office. Along the way, he ran into Sybill Trelawney who had just been unceremoniously thrown out of the Room of Requirement. From her, he learned that Draco Malfoy had completed his mission and that Severus Snape had been the Death Eater who eavesdropped upon The Prophecy. In a huff, Harry questioned Dumbledore who did not wish to speak on the matter. When he was sent to retrieve his Cloak of Invisibility, Harry told Ron and Hermione everything, gave them the Marauder's Map and his Felix Felicis, and ordered them to watch the castle.

Before they left, Dumbledore made Harry swear to obey any order given him, regardless of his feelings about said order. Setting off from Hogwarts in the evening, Dumbledore and Harry appeared to head for the Hog's Head. Instead, they Apparated to just outside a cave by the sea, being unable to enter directly due to its protective enchantments. In order to reach the cave, they had to swim through the swirling waters among the rocks. Once inside, Dumbledore attempted to locate the Horcrux's second line of defence. He spoke in a whispered tongue that Harry could not understand. He found a hidden doorway which only opened when it received an offering of blood. Dumbledore commented that he found this step barbaric and well below the standards he thought Lord Voldemort should have. They next found themselves in a vast chamber containing an underground lake, with a solitary island at its centre from which a faint green light was visible. After a failed attempt by Harry at Summoning the Horcrux, Dumbledore located a carefully concealed boat that would allow them safe passage across the lake. During the crossing, Harry learned another of the Horcrux's lines of defence; the lake was filled with Inferi, which would attack anyone who touched the lake's water. Dumbledore instructed Harry on the use of fire as the weapon of choice against the Inferi, should it become necessary.

Arriving at the small island, which was about the size of Dumbledore's office, they found a basin filled with glowing green potion. This last defence could not be touched, parted, or scooped out physically, neither could it be made to change magically; someone would have to drink it to obtain the Horcrux that lay within. Dumbledore ordered Harry to help him drink all of the potion, no matter what effects it caused, even if Harry had to force it down Dumbledore's throat. Harry was initially reluctant to cause his mentor such great pain, but when Dumbledore reminded him of his promise, he relented. While Dumbledore drank it, he had visions of the duel between him, his brother Aberforth, and the Dark Wizard Gellert Grindelwald that led to his sister Ariana's death. When they finally finished the potion, Harry attempted to conjure water for Dumbledore with an Aguamenti charm, but this proved ineffective as the water disappeared before Dumbledore could drink it. This being another defence designed by Lord Voldemort. In desperation, Harry filled a cup with water from the lake. As he splashed it on Dumbledore's face, Harry felt something ice cold on his arm and saw a disgusting hand and the Inferi climbing up from the lake. Harry panicked and attempted to fight back with a multitude of spells and curses, including Impedimenta and Sectumsempra, but none of them worked since the Inferi were too numerous and could not feel pain. He was overwhelmed and dragged under. Dumbledore, having regained consciousness, created a ring of fire around them that repelled the Inferi. He pocketed the Locket and drove the Inferi back into the lake while he and Harry escaped in the boat.

Noticing that the fire was costing Dumbledore all his strength, Harry supported him once back ashore. When they reached the right place, Harry used a small cut on his arm to reopen the hidden doorway. As they proceeded, he was increasingly worried about Dumbledore's weakened state as he helped Dumbledore back to the rocks outside the cave, and he sought to reassure his headmaster. Once among the rocks, Harry Disapparated them back to Hogsmeade.

Return to Hogwarts and Battle of the Astronomy Tower
Once back in Hogsmeade village, Madam Rosmerta alerted Dumbledore that the Dark Mark was hovering over Hogwarts. This seemed to invigorate Dumbledore. She lent Dumbledore and Harry two broomsticks, and they flew back to Hogwarts, Dumbledore lifting the protective enchantments cast over Hogwarts so that they could enter at speed. While they were flying, Harry could not help but worry for his friends that he had asked to watch the castle. He worried if it was his fault that someone had died again. When they arrived atop the Astronomy Tower, no one was there. Dumbledore needed help quickly, and Harry wanted to go get Poppy Pomfrey, but Dumbledore asked specifically for Severus Snape.

The mark was there, because, Draco had finally fixed the Vanishing Cabinet and introduced Death Eaters into the school. However, the Death Eaters met resistance in the form of members of the Order of the Phoenix and Dumbledore's Army and fighting broke out. The Dark Mark was not placed above the Astronomy Tower, because they had killed someone; it was a trick to lure Dumbledore back to the school faster. However, Death Eater Gibbon was killed accidentally by Thorfinn Rowle and Bill Weasley was also brutally attacked in the fighting by Fenrir Greyback, even though it was a not full moon. As such, Bill would not ever be a full werewolf, but would have some wolfish tendencies such as a taste for raw meat.

When they heard footsteps, Dumbledore ordered Harry, who was wearing his Invisibility cloak, away from the door and put a Full Body-Bind Curse on him when the attacker burst through the door. Draco disarmed Dumbledore, but did nothing else but talk as the time ticked by. While standing atop the tower, they discussed how Draco had almost killed two other innocent students over the school year and that Draco was not a killer. Other Death Eaters soon joined Draco atop the tower, but nobody did anything, as it was Voldemort's order for only Draco to kill Dumbledore. Snape soon joined them, and killed Dumbledore after the latter begged him. Freed from the Body-Bind, Harry pursued Snape through the chaos of battle. He finally caught up with him around Hagrid's hut. He repeatedly cast spells at Snape, but they were all deflected by the more powerful wizard. When Harry attempted to use Sectumsempra, Snape revealed that he was the Half-Blood Prince, cursed Harry so that he could not respond, and escaped with Draco.

Aftermath
Walking back from Hagrid's Harry tried to tell him what had happened, but Hagrid refused to believe him. When they reached the spot where Dumbledore's body lay, Harry broke down next to it and refused to move until Ginny Weasley lead him away. While he was there, Harry noticed that the locket they had obtained from the cave was not Salazar Slytherin's. The "Horcrux" was a fake. Finding a cryptic note inside from an "R.A.B.", Harry kept the locket, not because it was valuable, but because of what it had cost to obtain it.

Dumbledore was laid to rest on the grounds of Hogwarts School. The ceremony was attended by numerous witches and wizards including many from the Ministry of Magic that had not particularly cared for Dumbledore such as Dolores Umbridge. During the ceremony, many tributes were paid to the great wizard and he was encased in a White Tomb. Afterward, Harry made plans to eliminate the remaining Horcruxes, Ron Weasley and Hermione Granger vowed to accompany him.

Appearances

 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Half-Blood Prince (film)
 * Harry Potter and the Half-Blood Prince (video game)
 * Harry Potter and the Deathly Hallows