A/N: Extract is from Harry Potter and the Half-Blood Prince by J. K. Rowling, page 576. The rest is mine, although the characters are not.

Shout out to Emiliya Wolfe for beta-ing and providing inspiration with her fic 'A Tale of Two Sides'.

The Last Known Survivor

"Crucio!"

As Mulciber screamed, having dared question the Dark Lord's plan, Regulus took a chance and looked up at the Dark Lord from beneath the hood of his cloak. By candlelight, the Dark Lord's eyes glittered like rubies. Regulus dropped his gaze to the Dark Lord's fingers, wrapped lazily around his wand as if he weren't torturing someone for voicing doubts. They were pale and thin, nails pointed… Regulus shuddered. It was unnatural, what the Dark Lord had done to himself. He could appreciate power, he could appreciate magical experimentation… but if the Dark Lord had warped his soul as Regulus suspected, then he'd crossed a line that not even a Black would dare to.

"Does anyone else care to offer me their opinion on the cleansing we'll perform in ten days time?" the Dark Lord purred. Regulus stared at his feet and thought desperately of potions ingredients. He had been Crucio-ed last week for the 'vacant look on his face' and couldn't risk more punishment. He'd felt something crack inside him… all of a sudden it hadn't mattered that his family worshipped the Dark Lord… Regulus hated him with a fervour he'd never felt before.

"Well?"

He needed ruby dust, to hide him from the Dark Lord's sight; the tongue of a bull, to hide his name from being spoken; beeswax, to hide him from the Dark Lord's hearing, and chalk or perhaps marble, to hide him from the Dark Lord's magic… these were the ingredients for the potion he was working, the potion that would set him free.

"Avery… there is a surly look on your face. Do you have something to say? No… Crucio!"

Regulus gritted his teeth and ran the ingredients through his mind, trying to block out Avery's screams as he was tortured. He only had to survive a little longer. Ruby dust, the tongue of a bull, beeswax, chalk… Ruby dust, the tongue of a bull, beeswax, chalk...

The night was dark, the stars hidden by clouds, and the moon was a thin sliver in the sky, providing scant light for their gathering. The Death Eaters circled the Dark Lord, each stood where he designated them, each touched by his Mark. Regulus's burned as if he'd been branded mere seconds ago, throbs of pain fluctuating with the magic saturating the air.

"I have explored the path that leads to immortality further," the Dark Lord proclaimed, his speech of several minutes coming to a close, "Further than any have gone before."

Regulus swallowed, clenching his hands into fists to hide them from shaking. Across from him, he could make out Barty's shining eyes, fervid in their devotion. He'd once looked the same.

Taking a breath, Regulus pushed all thoughts of treachery from his mind. He could not afford to look any different. Not tonight, when all he had to do was survive. The potion was brewed; he was ready to leave. After this evening, he'd be gone, with only Kreacher by his side.

"You, my trusted lieutenants, you shall be the ones that help me bring glory to the wizarding world once more. I am mightier than any other wizard alive… together, we are powerful and we shall bring down the institution that oppresses us!"

The Death Eaters cheered and Regulus echoed their cries of jubilation.

"To Hogsmeade!"

Cracks of Apparition rang through the air and Regulus promptly turned on one foot and Apparated. However, instead of following the Dark Lord to Hogsmeade, he went to clearing half a mile away. Immediately he drew up his sleeve and began chanting over the Dark Mark.

"Kreacher!" he cried. His elf appeared with a pop, holding out a potion. The nature of the rubies made it sparkle even in the half-light. Regulus choked it down and jabbed his wand into the Mark, hissing as he sliced it open, drawing a crude circle around the Mark in his own blood. The snake hissed, then faded, the perpetual pain fading too… Regulus sunk to his knees with a sob. He'd done it. He'd stopped the magic of the Mark; the Dark Lord would not be able to find him now—he would be presumed dead.

For a heartbeat, Regulus considering going after the Dark Lord's Horcrux, protected somewhere so foul that Kreacher had nearly died while assisting him hide it. Then he snorted, dismissing the thought. He was far too much of a Slytherin… too much of a coward to risk his life going after a piece of the Dark Lord's soul. Regulus was a survivor and down that path lay certain death. That was Dumbledore and the Ministry's problem now.

"Come, Kreacher. Pass me the Portkey. We're leaving," Regulus said. "We're going to the Black property in France."

With his mother dead and his brother estranged, all that was left for Regulus to do was run.

Still slashing at the air with his wand, Harry yelled, "Sectumsempra! SECTUMSEMPRA!"

But though gashes appeared in their sodden rags and their icy skin, they had no blood to spill: They walked on, unfeeling, their shrunken hands outstretched toward him, and as he backed away still farther, he felt arms enclose him from behind, thin, fleshless arms cold as death, and his feet left the ground as they lifted him and began to carry him, slowly and surely, back to the water, and he knew there would be no release, that he would be drowned, and become one more dead guardian of a fragment of Voldemort's shattered soul…

Then Harry jerked as a sudden flash of light illuminated the chamber they were in, blazing above them. The Inferi flinched away, but still clung to him, pulling him closer and closer to the water…

"Shit, I'm too late," a voice muttered.

"Help!" Harry cried, uncaring if they were enemy or friend. "Please, help!"

A plume of fire seemed to fall from above, scorching the Inferi around him. Of course—how could he have been so stupid to have forgotten? Harry squirmed free as the Inferi milled in confusion, shying from the flames, raising his wand and casting, "Incendio, Incendio," and the Inferi bumped into each other as they tried to escape the blaze.

"What are you doing here alone?"

Harry looked up to see a figure flying on a broomstick, an arm outstretched. He'd never been more grateful to see a broom in his life. He had been sure that he'd failed, that he'd die and Dumbledore would die as well after suffering such torment.

"I'm not alone," Harry said, swallowing a sob.

"Indeed, he is not," Dumbledore added, his voice as brittle and sharp as glass. Through the flames, Harry could see Dumbledore stagger to his feet, raising his wand and a crimson and gold ring of fire circled them both, driving the remaining Inferi away.

"Bugger," said the man on the broomstick. "Err, hello, Dumbledore."

"Who are you?" Dumbledore demanded. Harry could see him wavering and moved closer, wand raised, in case he needed to help. For a moment, Harry though the man on the broomstick might flee, then he sighed and the broom dipped, bringing him down to the island they were on. The man had been wearing a hooded cloak, which he threw back as he strode forward with such aplomb that Harry thought Snape would be jealous of the theatricality. On closer inspection, the man had silver eyes and dark cropped hair. There was an angular tilt to his jaw that reminded Harry of Malfoy and a smirk on his lips that Harry had only ever seen in memories of a young Sirius.

"Regulus Black," Dumbledore said. Harry bit back a gasp and stepped closer.

The man—Regulus—nodded.

"But you died," Harry blurted. "Sirius—he said that you were dead. That Voldemort killed you."

"You're Harry Potter, then, are you? Well, if the Dark Lord knew that I was still alive, I suspect that he would very much like to Crucio me to death," Regulus said. He drew up his arm and bared a Dark Mark. Harry swallowed, backing away. Against Regulus's pale skin, the Mark vividly stood out, but the edges of it seemed oddly distorted.

"You have found a way of blocking him?" Dumbledore asked, sounding curious, then he staggered, groaning as he clutched at his side.

"Professor!" Harry gasped, rushing to his side. He helped prop Dumbledore up, wrapping an arm around his waist.

"You drank the Draught of Nightmares, then?" Regulus said. "Here, drink this." He thrust a potion into Harry's hands. It gleamed like the sunset, first pale shades of pink and orange, then darker shades of ruby and crimson, then it turned a liquid gold like molten sunshine. Harry looked from it to Regulus, then at Dumbledore, who's eyes had glazed over once more. Regulus was busy with the basin, scooping up the locket they'd come to retrieve and substituting it with an identical copy. Then he withdrew another vial from his pocket and poured it over both locket and basin. It was a sickly green… the basin began to fill as it had before. It looked as if nothing had changed.

"That should do the job," Regulus said with a note of satisfaction. He turned back and frowned when he saw Harry clutching at the potion. "It's the antidote. Go on, give it to him."

"Go on… Harry," Dumbledore rasped from his side. "We will… have to trust him… go on."

With shaking hands, Harry uncapped the potion and poured it into Dumbledore's mouth, taking care not to spill a drop. Dumbledore sighed, his eyes fluttering closed.

"Sir… sir! Are you alright?"

After a moment, a faint smile flickered across Dumbledore's face. "As right as I'll ever be… I suspect." Colour was beginning to return to his cheeks and he was leaning less on Harry. Relief made Harry giddy and he smiled in return.

"What else is he suffering from? He should have recovered more quickly," Regulus snapped. "Wait, no, this is not the place for this discussion."

"I concur," Dumbledore said. "I suspect you have quite the tale for us, as well. Can I trust that you will not flee with the locket?"

"On my honour as a Black," Regulus said, pressing his fist to his chest.

Dumbledore seemed satisfied with that, so Harry had to be. He helped Dumbledore into the boat and Regulus flew above them as they made their way across the lake, the Inferi left behind, still trapped in a circle of flames. By the time they had reached the entrance, Dumbledore seemed to have returned to his formed heath, his gaze shrewd as he looked up at their unexpected companion.

"Take care, Harry. Tonight, all may not be what it seems."

Before Harry could decipher Dumbledore's meaning, he was striding forward, opening up the cave wall and ushering them through.

"I will Apparate us to dry land and then I would like an explanation," Dumbledore said, offering his arm. Harry took it, and after a moment's hesitation, Regulus did too. With a twist and jerk of movement, they were back on the clifftop from where they'd started the night's adventure. Harry took a breath, then released it, finally feeling his racing heart begin to slow.

"There's no grand story," Regulus said. "I discovered the true nature of the Dark Lord and it scared me, so I fled. I was just trying to survive. My brother… imprisoned… my family… in ruins… what was there here for me to return to? But when I heard that he was back… had it confirmed… I had to do something. The Dark Lord claims to be immortal… I'd like to see him survive a Killing Curse once we've destroyed this." A fierce look of jubilation crossed Regulus's face. For a moment, it was like looking at Sirius's twin: that same drive for revenge burning everything else away until it was all that was left of them.

"It's not the only one," Harry said with a heavy heart. A devastated look crossed Regulus's face.

"What? No… that's impossible…" he whispered.

Dumbledore placed his hand on Regulus's shoulder. "Do not be disheartened. We have already destroyed several Horcruxes between us and with this one found, we will have destroyed another. I would love nothing more than to take the time to discuss the details of what has happened to you, but I fear we must return to Hogwarts, for the hour is late and Harry is not yet even seventeen." Dumbledore's eyes twinkled as he glanced over at Harry and it lessened the blow of his words.

"Very well," Regulus said, releasing a sigh. Then, as Dumbledore withdrew his arm, Regulus snatched out and grabbed his wrist. "What… how did you survive this?"

Harry moved forward, only to catch sight of what must have shocked Regulus—Dumbledore's blackened hand. It had spread further up his arm, the flesh dark and rotted.

"Ah, I was able to hold the curse at bay for a short while, you see, and Severus is a most excellent potions master," Dumbledore said.

"But not so well-versed at removing dark curses," Regulus remarked. "Were you not able to find a counter?"

"I did not believe that one existed…" Dumbledore murmured.

"What—you mean… sir… you cannot mean…" Harry trailed off, unsure what today. Surely Dumbledore could not be dying. It was like claiming that the grass was blue and the sky was green—simply impossible.

"Alas, Harry, I have lived a long and fulfilling life…"

"And you'll keep living it for a little while longer," Regulus interrupted. "With your permission? You are needed to help win this war."

Dumbledore drew himself up to his full height, his eyes flashing as if in anger, then he caught his breath and seemed to sag. "Very well. If you believe that there is something you can do."

Regulus seemed to hesitate, then he bowed his head. "I helped the Dark Lord invent this curse… I believe that I can reverse it."

Harry fought not to gasp as he watched Regulus work. Before his eyes, Regulus began casting a long, wordy spell with several intricate, complicated wand movements, and the withered flesh on Dumbledore's arm seem to slough off in ripples, only to be replaced by new, pink, healthy skin. It seemed from the way that Dumbledore grit his teeth that the spell was painful… surely a little pain was better than the alternative, however. Finally, the spell was over, and Dumbledore's arm was fully recovered.

"I am most grateful…" Dumbledore said. Tears glimmered in the corners of his eyes. "As much as I am ready for the next great adventure… there is much more yet here for me to do." He looked over at Harry. "So much for me to say."

"You may contact me through Kreacher," Regulus informed them. "He always knows where I am."

"I will ensure that we will speak as soon as possible," Dumbledore promised.

With a crack of Apparition, Regulus was gone. Harry blinked, staring at the empty space where he'd been before turning to Dumbledore.

"Sir… did that… are you okay? Were you really… would that have really killed you?"

Dumbledore seemed to age before his eyes. "It would have, Harry. I am sorry for not being more honest with you. It was something that I did not wish to burden you with."

Harry burned with the unfairness of yet another thing Dumbledore had not told him, but pushed down his anger until it was nothing but ash. Dumbledore had his reasons, as Hagrid would say, and Harry had to do his best to trust them.

"Let's return to Hogwarts, sir," Harry said. "I'm glad that you're alright."

"Let's return," Dumbledore agreed. He looked to the sky and a troubled expression crossed his face. "The moon is almost full, tonight."

Harry looked up and frowned. The moon blazed brightly for a moment before disappearing behind a cloud. He wondered if Lupin was alright. He hoped his friends had stayed safe. Most of all, he thought of Sirius, and hoped that Sirius could see his younger brother from beyond and be proud of him.

"Here." Harry took Dumbledore's offered hand. In the moments before they Apparated, he glanced around the barren, desolate clifftop, and felt nothing but pity for the boy who'd been desperate enough to hide his soul here.

With crack, the pair disappeared.

Everything had changed.

Word Count: 2725 (incl. extract)

QLFC Round 10 Chaser Three Prompt: Regulus Black died during the war. Reverse his fate.

From the prompt: If a character died in canon, you will write a story where they survive the war. Whether you focus on the moment that changed whether they lived or died, or you show the impact, the aftermath of their fate through someone else's eyes, or whatever is entirely up to you.

Optional Prompts

6. (colour) Ruby

7. (song) Eye of the Tiger by Survivor from which I've taken then line "Just a man and his will to survive"

9. (spell) Crucio

If Regulus feels a little 'over-powered' to you, I posit that we've hardly seen what an 'average' witch or wizard can do. Regulus was initiated into the Death Eaters, Voldemort's inner circle, at age sixteen. To me, this suggests that he was unusually talented. As Sirius is always lauded as a talented dueller and it's implied that he was one of the smartest in his year (Animagus by sixteen!), it stands to reason that studious, quiet Regulus was just as smart, if not cleverer. Since then, all he's done is plot ways to protect himself and bring down the Dark Lord, should he truly be as immortal as he claimed. Hence, powerful Regulus—what fun he is to write!