He didn't know when things changed so drastically.

Once upon a time, he had been a true scion of the House Black, respected by everyone. And now he was reduced to groveling at the feet of a madman who wasn't even of pure blood, thanking him every time he was tortured.

Barty was lost to the devotion of the Dark Lord, Sirius hated him, and the only thing his parents cared about was what a good little Death Eater he was.

Regulus Black hated Voldemort with a burning passion. Because of him, he had lost everything.

Had he been a Gryffindor, he would probably have done something stupid, like attack him directly. But Regulus was a Slytherin, so he plotted in secret, spending hours upon end trying to figure out Voldemort's weakness, all the while keeping up the pretence of being a loyal follower.

But no matter how much he searched, he never found it until Voldemort needed his help. It was rather ironic, the fact that it was Voldemort who had caused his own downfall.

He needed a House-Elf, he said. So Regulus lent him Kreacher, the one elf who was loyal to him over his mother, the only one who would not report what had happened to his mother if he ordered it so. And then, he waited.

When two hours had passed, he felt that Kreacher had had enough time to complete whatever task it was the Dark Lord had assigned for him.

"Kreacher!" he called out in the quiet of the room.

Immediately, the elf popped into the room.

"Master Regulus!" he cried, flinging himself at Regulus' feet.

"Stand up," Regulus told him. His bowing reminded him uncomfortably of how the Dark Lord expected his followers to act. Once the elf stood up, Regulus started his questioning. "What did the Dark Lord have you do?" he demanded.

Kreacher shuddered. "The Dark Lord, he – he had Kreacher try to get a locket for him. Kreacher – Kreacher had to go inside a cave by giving his blood. Oh Master Regulus, it was horrible! The Dark Lord made Kreacher stain the rock dark red! Oh, Kreacher would have to scrub it for days and days to get all the red out! And then – oh Master Regulus, he had Kreacher sit on a boat in a lake. Kreacher does not know how a lake got inside a cave Master – there was rain to give it water! It was cursed water, Master. Kreacher saw dead Masters and Mistresses in the water, and they were moving! And then – then he had Kreacher drink poison. It burned, Master, it burned! And after Kreacher had drunk the poison, the Dark Lord went away and left Kreacher there. Kreacher thought he was going to die, Master Regulus. Kreacher would have died if Master had not called for him! It was horrible, Master, so horrible that Kreacher does not want to say," the elf babbled, the entire tale coming out in one long speech.

"Did you see the locket Kreacher? Tell me about it!"

"It was a golden locket Master. It had the symbol of the noble house of serpents on it, just like Master Regulus used to wear when he went to Hogwarts."

"Thank you Kreacher," Regulus told the elf as a dismissal.

Once the elf had disappeared, Regulus made his way to the hidden library his father had kept. It contained books on the Darkest of the Dark Arts, and he faintly remembered reading something that might explain the Dark Lord's need to protect a simple locket so securely.

He pulled out The Ancient Arts For Gaining Power and ran his finger down the index. There it was – Horcruxes.

It all made sense now, why the Dark Lord was seemingly invincible, why he insisted that he had gone further on the road to immortality than anyone else ever had. He wasn't a pureblood, he couldn't have known about the history of Horcruxes. He must have believed that he was the only person to make one in history.

Voldemort had handed his one weakness to Regulus on a silver platter. Once his Horcrux was destroyed, Dumbledore and his Order could kill him easily. It would take time and money, but Regulus had an abundance of both those things.

Voldemort thought he was the pupeteer holding Regulus' strings, but he wasn't. Regulus had broken free of him a long time ago.

He had stolen everything Regulus held dear – his name, the man he loved, the love of his brother – and in return, Regulus would ensure the loss of the only thing the Dark Lord held dear.

His life.

For:

Fanfiction Tournaments (May)

Dueling Tournament

The If You Dare Challenge, Prompt 617. Daring Revenge

Colors Competition, Black (negative)

Greenhouses Competition, Gillyweed

Fantastic Beasts Challenge, Sharke