Disclaimer: I do not own Harry Potter.
Regulus Arcturus Black sat at the writing desk in his bedroom staring off into space. So much had happened in the last few weeks. It hadn't really been that long since the Dark Lord had last used his house as a home. The night Regulus had decided to rebel.
Even before that night, Regulus had begun to have suspicions about the Dark Lord. Everyone knew he was evil; the Slytherin house was full of children boasting about the crimes their parents had committed in the name of the Dark Lord. Students were lining up every year to break some school rule and prove to him that they were up to the task of being a Death Eater. The little social club was definitely alive and well in the school. Even Regulus had looked up to the blonde giant a few years ahead of him, trying to be exactly like Lucius. Regulus laughed. Look at the coward now, trying desperately to kiss up to the Dark Lord lest the master get angry. Well, Regulus was different.
He wasn't sure why he was so naive back at school; how he could have missed the idea that being a Death Eater wasn't about breaking some trophies in the trophy room. He seemed to expect that he would be breaking into banks and stealing things for the rest of his life. The thought had excited him. But his first mission was to kill, as was every Death Eaters.
It's not that Regulus was against killing, it was almost a requirement of Slytherin House to be in favor of it. But Regulus was against killing innocents. And Regulus was sent to kill a muggle just because they lived too close to a wizard. He didn't like it, but by then he was in too deep. By then, to say no was to sign your death warrant.
Regulus reached for a piece of parchment on which he had written a note to the Dark Lord. No, to Voldemort. Regulus was going to die, might as well say the name. Yes, he was rebelling against Voldemort; but he wasn't going down alone. Voldemort had trained him to be a killer, and that's what he was going to do if he could.
His plan was hatched when Michael Watson had lent him the book on Horcruxes. It certainly fit for how Voldemort could be immortal as he boasted and seem to be so inhuman. Regulus had actually thought the crazy thought that Voldemort may have made more than one Horcrux, but he had brushed the thought aside quickly. No one was stupid enough to try that. But Regulus did know where the horcrux was; and that information was the last straw.
He remembered the night well. Voldemort had taken his elf for a mission a few hours earlier. The elf returned to Regulus after Voldemort was done with him, as ordered, but he was incredibly weak and screaming for water. After some time, Regulus got Kreacher a little better and laid him down to rest. And then Kreacher began to recount the story: a cave with many and powerful magical defenses, where Voldemort had cut Kreacher to breach them, a vast lake with something white and dead disturbing the deep, a small island with the glowing potion in a basin, the locket which Voldemort had placed inside the basin after making Kreacher drink the vile concoction, the part where Voldemort left the elf to die on the island.
And so the plan was born, leading to now when Regulus grabbed a locket he had recently purchased and slipped the note inside. He took several deep breaths and called his elf, the elf appearing at his side immediately.
"Kreacher, take me to the island where Voldemort left you to die," he said. Kreacher looked at the locket in his hand and began to shake his head. Regulus thought about how horrible the event had to have been to be powerful enough to fight the ancient elf magic, but Regulus repeated himself and Kreacher was left with no choice but to grab his master's hand and apparate.
Regulus' eyes adjusted to the strange lighting after a few moments. He was standing on a small island in the middle of a sea of water large enough that he couldn't see the edge. The space was clearly in a cavern of some kind because it was pitch black except for a blinding, green light coming from a small basin on a platform in the middle of the island. Regulus walked up to the platform, aware of the elf cowering in fear behind him. He could see the potion in the basin and attempted to vanish it. It didn't work, not that he had thought it would, but it was worth a try.
"Kreacher," Regulus said softly. "You will make me drink this potion, all of it, and then you will take this locket and switch it with the one inside the basin. Then you will take that locket and destroy it. Do you understand me?"
"Master?" Kreacher said.
"Kreacher, yes or no?"
"Yes," Kreacher said.
"Good. Now, I may tell you to stop feeding me the potion after you have begun. Do not follow this request, is that understood?"
"Good. One final order. You are to leave me after you switch the lockets," Regulus said.
"But master, you'll die," Kreacher said.
"I know," Regulus said. "But it will be far better to die here than to live for what Voldemort would do to me. Promise me you won't try to save me. Destroy the locket; that is how you honor me."
"Yes, master," Kreacher said through tears.
Regulus nodded and handed his locket to Kreacher. Then he conjured a large cup and told Kreacher to begin. Kreacher filled the cup with the potion and began to feed it to Regulus.
The world no longer existed. His vision blacked out. Pain was all he knew, pain through every inch of his body. Pain even worse than the Curciatus Curse his mother used to use on him. He wanted nothing but for the pain to end. He could hear himself crying out for it to stop.
His chin was lowered and another cup was pored in. The pain stopped. He was standing in a field with his arms and legs bound. A man stood in front of him facing away from him. In front of the man was a woman that Regulus recognized immediately: His mother. He tried to cry out to her, but his voice wouldn't come. She looked longingly at him like she was expecting for him to do something. He squirmed, but he couldn't move. Suddenly the man turned around and Regulus recognized the face of his master. "Surely you knew this would happen," Voldemort said. Then he turned around with a grin and shouted "Avada Kedavra!"
Even before he saw his mother hit the ground, he felt his chin being tugged open again. The pain was returning, but it was almost as if he was nummed. His vision had been transported to a boiling hot room. Fire rolled down the sides like Hell itself. Voldemort again stood between him and a victim; except this time it was his cousin and role-model Bellitrix Lestrange. She had been tied to a large metal board which Voldemort had at wand point. He turned back to Regulus, who tried but couldn't move. "Just say the word and I'll stop. Say you'll die now and leave my sanctuary alone." Regulus tried to speak, tried to save his only real family, but he couldn't do it. Voldemort had betrayed him. He had to go through with it. "Pity," Voldemort said as he moved his wand and the metal slab slammed, body first, into the fire.
Regulus' chin moved again and he knew what was coming. The pain returned in full force, but he was more worried about who would die next. He knew there wasn't much more potion; therefore, this would be the person that would mean the most. This would be the one who would convince Regulus to turn back. He closed his eyes. Finally he couldn't stand it any longer.
He was standing in a massive, stone indoor arena, facing the floor. In the middle of the floor was a stone dais with a long, flowing black curtain hanging and gently swaying though there was no wind. Again, Voldemort stood facing away from him, but Regulus was looking out over the victim. Regulus forced himself to look down. The site surprised him more than anything else that day. He was staring at the smiling face of his brother. Before Voldemort could say anything or do anything, Sirius smiled at his brother and said "I chose to fight. Stay strong and finish. I promise you will not have died in vain brother." Then he turned and ran into the center of the stone dais and vanished amid Voldemort's angry cries.
The vision was broken as Kreacher approached with the final cupful. Regulus allowed the potion to be poured down his throat, but felt no pain, no visions, and no loss almost as if something was protecting him from the potion's effects. Once it was finished he ordered Kreacher to switch the lockets and leave. The elf did as ordered.
Regulus knew what would happen now, but he didn't have much choice. He would die now, quickly and easily, or he would die later in anguish at the hands of Voldemort. He chose to die now. He stood up and dived into the water. Before he had descended ten feet, hands grabbed him and began to tug and pull at every inch of his being, dragging him further and further into the lake. He only had time to look longingly back up at the faint light above him and think, "You promised brother, I'll hold you to it." Then the world went black for the last time.