Fireman
Harry mentally replayed his interaction with Avery over and over again in his mind as he stood in the Chamber of Secrets, often flashing back to his interaction with Tom Riddle's diary.
"For Bellatrix, I give you Hufflepuff's cup."
"For Lucius, an enchanted Diary from a different age."
"And for Regulus, the locket of my ancestor, Salazar Slytherin himself."
Diary, Locket, Cup.
Harry memorized the interaction, running the images over and over again in his mind. He had already destroyed the Diary, owned by Lucius, leaving Hufflepuff's cup and Slytherin's Locket. They were respectively owned by Bellatrix Lestrange and Regulus Black.
Bellatrix Lestrange, formerly Bellatrix Black, Sirius' cousin.
Regulus Black, Sirius' brother.
Both of them were members of the Black family, Harry noted, and even Lucius Malfoy's wife was once a member of the Black family.
"Kreacher!" Harry called out, and suddenly realized his mistake. He didn't know if elves could access the chamber, but Kreacher appeared anyways.
The old elf popped in, looking around warily at the Chamber of Secrets. "Half-blood master calls?"
Harry rolled his eyes. "What can you tell me of a locket owned by Regulus Black?"
The elf winced as if struck, before gaping at him. "H-How could master know?"
Harry's brows raised. "So you know of it?"
The elf nodded hastily. "Master Regulus commanded Kreacher to destroy the Locket as his final wish. Kreacher has been unable to accomplish his dying command."
"Do you have it?!" Harry demanded hastily, and the elf nodded quickly. "Bring it here and I will destroy it."
He barely finished speaking when the elf popped away, reappearing only moments later with the locket. Harry grabbed it, and saw it was the exact locket from Avery's memory. "Kreacher, do you know what exactly this is?"
Kreacher shook his head. "Only that it is important to the Dark Lord. Master Regulus wanted the Locket destroyed as his dying wish."
"I see." Harry replied, feeling mildly disappointed. If it was anything like the Diary, there was no way he would put it on. "Do you know anything about a cup given to Bellatrix?"
Kreacher shifted, "Mistress Bella had many items, most were moved to her vault."
Her vault? He must mean Gringotts. "Can you access her vault?"
Kreacher shook his head, and Harry internally cursed.
Narcissa Malfoy is Bellatrix's sister. Harry frowned, remembering how he had killed both her husband and son. Maybe she can access Bellatrix's vault?
"Can her sister access it?"
"Kreacher is unsure." The elf shifted. "Why does master want to access Mistress Bella's vault?"
Should I tell him? Harry decided he would, at least partially. "The item that Regulus was given is part of a set, all of which he would want destroyed if he knew about them. I suspect that Hufflepuff's cup is one of these items, and it is in Bellatrix Lestrange's vault."
"Kreacher understands." The elf nodded. "I shall speak with Mistress Cissy, and see if she can obtain Mistress Bella's cup."
"Wait-" Harry started, but the elf apparated away before he could finish. Hopefully he doesn't mess up my plan.
He looked at the locket in his hand, and wandlessly summoned a basilisk fang from across the room. Time to destroy this thing.
