WARNING: Very history heavy.
The two Hogwarts students sat quietly and uncomfortably as Dumbledore paced his office in deep thought. Luna had decided that it was perhaps best not to question the Grey Lady and proposed to ask Dumbledore to do it instead.
"You're sure the diadem was a Horcrux?" he asked, abruptly turning towards them.
"Yes," Draco spoke, teeth gritted in frustration, having had to explain everything several times. He wasn't a storyteller, and Dumbledore knew this. Either Draco's patience was being tested or Dumbledore had some reason to doubt that a Horcrux was successfully destroyed.
"Before you went to the Gaunt shack with me," the headmaster spoke, suddenly changing the subject, "do you remember that I told you I would show you the real memory of Morfin Gaunt?"
Draco nodded, even though he didn't actually remember.
"Well, perhaps I've got a better memory for you. You don't need to see it, it's quite dull, I'm afraid. But its contents are quite important so I'll describe it."
Dumbledore walked back to his chair and sat down.
"It still seems like it was only last week," he began, "that I met Tom Marvolo Riddle. I was to speak with Mrs. Cole of Wool's Orphanage upon Tom Riddle's admittance to Hogwarts. The director of the orphanage informed me of certain incidents that involved Tom. I was directed to the boy's room, where I convinced him to return all objects he'd stolen from others after demonstrating my own magical ability. I invited him to attend Hogwarts and gave him the information he needed. Perhaps Tom was feeling less different after learning the truth about why he was able to do certain things without trying, so he told me he could speak to snakes."
He paused before continuing, "I believe that his past is very important to him, and so it is crucial we study it. This memory, for instance, shows that Voldemort had a knack for collecting trophies. I have shown Harry this memory, and others that explain why Draco and I were at the Gaunt shack."
"So he knows which side I'm fighting for?" Draco said. "Isn't that dangerous?"
Dumbledore smiled. "All knowledge is dangerous, just as anything powerful is. Fortunately, you have no need to worry." Returning to his previous subject, he said, "The Horcruxes we've had so far are valuable trinkets in their own ways. The diary was a means of re-entering the school; the ring connected the Gaunts to the Peverells; the diadem is the prized artifact of the Ravenclaw community.
"I suppose it makes sense that he chose the diadem. He was quite taken with his magical background and managed to procure esteemed objects from Slytherin and Hufflepuff as well. Mister Malfoy, you may not enjoy storytelling, but I hope you are quite alright with listening."
Draco gave a slight nod and waited for Dumbledore to start.
"Let us begin with Bob Odgen. He was a wizard employed by the Department of Magical Law Enforcement. He traveled to the Gaunt shack to call forward Morfin about magic used to harm a Muggle, known to us as Tom Riddle Sr. During this meeting, Morfin attacked Odgen while his father abused Merope. After saving Merope from the Revulsion Jinx, Odgen left the shack and returned with enough forces to take Morfin and Marvolo to Azkaban. I saw this in Odgen's memory, and perhaps the most important thing in it was that Marvolo had in is possession his ring and the locket of Slytherin, but he held or wore neither as he was escorted away from his home."
"That's how you knew you might find the ring there," Draco realized.
"Shouldn't the locket have been there too?" Luna said. "Unless Voldemort went back and took it somewhere else for fear of keeping two Horcruxes so close together."
"A good guess from both of you, but not accurate. Tom Riddle acquired the locket from a woman who purchased it from Borgin & Burkes, to whom it was sold by Merope Gaunt. You see, when I looked at Morfin's memory, I saw his encounter with Tom. Morfin explained the Marvolo was dead and that Tom's true father was a Muggle. Merope had seduced the muggle with a love potion and made the mistake of quitting to use it on him after a long time. He immediately left her, prompting her to return to her family, only to steal Slytherin's locket. After this, the memory blacked out. When Morfin awoke, he was missing the ring he had with him. Across the valley, Tom Riddle Sr. and his parents lay dead. The Ministry suspected Morfin, who confessed without hesitation. It was in Azkaban that I found him and extracted the true memory but before I could provide the proof to the Ministry, Morfin had passed."
There was a moment of silence.
"It was Voldemort who killed them," Luna voiced.
Dumbledore nodded. "When he learned the truth, that he was a half-blood, he stunned Morfin before killing the Riddle family with Morfin's wand. He returned to change Morfin's memory and took the ring. Of course, all of this is just conjecture, but Voldemort most likely took the ring with him and waited to make it a Horcrux so that when the Ministry came, they wouldn't be able to detect the dark magic in the house."
"Just how many Horcruxes did he make?" Draco wondered aloud.
"At least five," Dumbledore said. "The three that have been destroyed, Slytherin's locket, and Hufflepuff's cup. We have no proof regarding the latter two, but I've seen yet another memory that suggests that they are, in fact, cursed with the dark magic. After completing Hogwarts, Tom Riddle found a job at Borgin & Burkes. One of their customers and sellers was a Hufflepuff pureblood named Hepzibah Smith, a collector of valuable magical artifacts. Hepzibah was visited by Tom one day, and she decided to show him two of her most beloved possessions: the cup and the locket. She informed him that Burke had purchased it from 'a ragged-looking woman who seemed to have stolen it, but had no idea of its true value.'"
"He knew right then it was his mother, didn't he?" Draco deduced.
"He did, and he believed the locket to be his birthright. Two days later, Hepzibah was found dead, her treasures gone. The memory I just recounted was that of her house-elf, Hokey, who was quite old and accused of accidentally poisoning her master, of which Hokey had a clear memory. I learned that this was another false memory and it was really Voldemort who took the cup and the locket and killed Hepzibah. You'll understand that it was unusual for someone as brilliant and academically successful as Tom to have chosen to work in Borgin & Burkes. Professor Slughorn himself encouraged the student to find a position at the Ministry, but Tom was much more interested in teaching Defense Against the Dark Arts here."
"The irony," Draco muttered.
"Yes, the irony," Dumbledore repeated. "After Tom began calling himself Voldemort, he returned to the school to discuss with me, the new headmaster, about taking the position. Of course, his army of Death Eaters awaited him at the Hog's Head and I made very clear to him that I was aware of this and wished to know his true desire for returning to Hogwarts. Furious, he cursed the teaching post and left. No teacher lasts more than a year in that position, as you have very well learned by now. And now, I understand that he only returned to hide the diadem. He arrogantly assumed that only he had known and would ever know about the Room of Requirement."
"I'd say it's on its way to being common knowledge," Luna said.
"One last thing," Dumbledore told them, "before I let you go. Draco, I told you I brought Slughorn here for a reason, not just to teach. There is a memory I have of him and Tom Riddle—a rather peculiar one, you see, for it has been tampered with."
"You think Voldemort took a Horcrux-to-be from Slughorn?" Draco asked.
Dumbledore shook his head. "Much worse, I'm afraid. The memory shows Tom Riddle questioning Slughorn after class about Horcruxes. After Tom mentions that word, the room fills with a fog as Slughorn demands, in an unnaturally loud voice, that Tom never utter that word and insists that he wouldn't tell Tom a single thing if he knew anything about Horcruxes. I will show this memory to Mister Potter and entrust him with collecting the true memory from Slughorn, who has already recruited Harry as a member of the Slug Club. Perhaps we'll be fortunate enough to learn what Voldemort discovered about Horcruxes."
"Seeing as three Hogwarts houses have relics that are now Horcruxes," Draco started, "we can assume that another Horcrux is a relic of Gryffindor."
"The sword is the only known relic, and it has always remained with me," Dumbledore said. "We are not a hundred percent sure that the diadem is a Horcrux, especially since it didn't try to kill you when you attempted to kill the piece of soul it may have contained. It is best that I keep the diadem. I will ask Helena Ravenclaw about it and about Tom Riddle. Thank you both for your help and I hope you have learned much today."
"Indeed," Draco affirmed. He and Luna left the office for a late lunch and decided that they'd had enough of magic and education for awhile.