Breathing in lungfuls of sea air, Regulus stood on a cliff, overlooking the vast, blue expanse. Led by the elf, he swam across the almost hidden stretch of relatively calmer water.

He pulled out the flask of blood he had brought along, and smeared it across the rock. He wasn't sure if dragon blood would work, (but if Kreacher's blood had worked the last time, there was a chance it would), and Regulus didn't want to make himself physically weaker before entering the blasted cave. Nothing happened. Smiling bitterly, Regulus pulled out his knife, and amid loud remonstrations from Kreacher, he sliced open his hand, and squirted the blood on the rock. It had to be warm blood, he reasoned, shaking his head slightly at the crudeness of the design. His contemplation about how far Tom Riddle would go to weaken his adversaries were put out of his mind when the outline of an arch suddenly blazed bright silver, and the rock simply vanished into nothingness.

Armed with nothing but his wand and a quivering elf by his side, the eighteen year old stepped inside; knowing exactly what horrors awaited him in the dense darkness within.

The vast, smooth, glass-like expanse of dark water stretching before them sent chills down his spine, he was not sure if it was the conspicuous powerfulness of the place, or the calm, ominous beauty of the dark, misty cave. He followed, his eyes on the distant green mist, as the loyal house elf led him to an unremarkable spot on the banks.

"Master has to pull on the snake-rope, and the boat will appear," said the elf, in a hoarse whisper. His huge eyes darted in all directions, as if he expected Voldemort to materialize from the blackness.

"Master Regulus, please come home. This is no place for a young boy."

"Kreacher, we had a deal. You promised."

The house elf could not come up with an argument against this obvious fact, and so stood there with his knees shaking so badly they were knocking against each other.

Regulus found the spot; it was difficult to describe, it was as though air had slightly congealed over the space. He closed his first around it and pulled out his wand with the other, teetering over the edge of the water. He tapped his fist with the wand, and at once, a ghostly green chain appeared out of nowhere.

It coiled around his hand, and made quite a loud racket as it raised a boat from the silky black water. The noise died down almost instantly, leaving the cave seemingly more silent than it had been before.

Regulus regarded the boat with a warily, like he couldn't believe it had been this easy. Wand at the ready, he stepped inside; followed by Kreacher, who was now regarding the water with the utmost loathsome he was capable of. As the boat's prow cleaved soundlessly through the still waters; neither of the occupants showed any signs of having seen anything alarming in the water below, though there had been quite a few.

As the boat glided to a halt; Kreacher tried, once again, to reason with Regulus. But whatever he wanted to say, whatever argument he had come up with since leaving the banks, the words died on his lips when he saw the blazing look in Regulus's eyes.

They disembarked; the unnaturally quiet house elf, and the lanky teenager whose pale face was now tinged an unnatural green from the glow emitted by the stone basin. He stepped closer to the source of light, the potion looked almost harmless, but Regulus knew better.

He reached out to touch the ghostly green liquid, but his fingers encountered a resistance, a protective cocoon of slightly denser air all around the phosphorescent surface. He tried to Vanish it, to Transfigure it, to simply empty it out, but it refused to budge.

He also knew what had to be done, having been wisely informed by a drunk Kreacher. He waved his wand in a sort of complex jiggle, and a crystal goblet materialized from thin air. The goblet sank through the dense air with no qualms of any sort.

"Remember your promise, Kreacher. Replace the locket as soon as the potion is over. Make sure I keep drinking, Kreacher, even if I beg you to stop. Do you understand? If I don't make it..."

The elf gave a strangled sort of cry at this.

As though he hadn't heard anything, Regulus continued, "If I don't make it back, destroy the locket. That is an order, Kreacher. Destroy the damned thing. I also forbid you from telling anyone in our family where I've gone, or what you know about this entire ordeal. Not even mother. Do you understand?"

The elf looked at him for a full minute before nodding slowly.

"Remember your promise. Make me drink the potion. And leave this place at the first sign of danger. Take the locket and go. And Kreacher?"

The elf looked at him.

"Don't come back."

At this point, the elf backed away slowly, tears leaking through his fingers as he covered his face, trying to hold them back.

Regulus took a deep breath and turned to the stone basin. He let his hatred for Voldemort flow through him, and plunged the goblet into the liquid. As he drained the second cup, he remembered the first time Voldemort had used the Cruciatus Curse on him for speaking out of turn. This was equally painful, if not more, considering he was doing this to himself.

He dropped to his knees, hands shaking terribly. The goblet rolled away, and the elf for a moment considered leaving it there. But he had been given a direct order, and it took him all of his strength to fight it. Against his will, the tiny creature picked it up, filled it with potion, and poured it down Regulus's throat, positively wailing as he emptied goblet after goblet into Regulus's mouth.

Each sip was a new nightmare, a replay of every horror he'd witnessed as a Death Eater—torture, death, and Voldemort's cold laughter. By the sixth goblet, he had collapsed, his body trembling as he writhed on the stone floor. Kreacher, sobbing, forced more of the potion down his throat, even as Regulus screamed for him to stop.

After the tenth cup, Regulus collapsed on the floor, his head filled with scenes of horror he had witnessed as a Death Eater; the helplessness with which he looked on, the panic he had experienced when he had found out to what lengths Voldemort was prepared to go to inspire fear; images of his brother on the floor, writhing in agony.

Regulus screamed in pain, a sound that haunted Kreacher as long as he lived. The liquid was almost gone now, his Master was whimpering in pain, curled up in a ball on the floor. As Kreacher filled the last goblet, he was seized by a thought.

He would not be disobeying any direct orders, and he could not bring himself to feed more to the young boy he had watched grow up. The elf straightened himself up, and with a steady hand, scooped up the remaining potion; and, with a determined look on his scared face, emptied the contents down his own throat.

He immediately doubled over in pain, but was conscious enough to carry out the order his young Master had given him. He picked up the locket, replaced it; and turned to see Regulus, to tell him they had done what they had come for, to tell him that they could go home.

All the blood drained from Kreacher's face when he saw where Regulus was. In his stupor, Regulus had dragged himself to the edge of the lake, groping for water. Kreacher watched, horrified, as Regulus's hand touched the inky blackness. He screamed a warning, too late, as a marble white hand broke the surface of the water; as though in slow motion, and closed over Regulus's wrist.

Regulus was jerked into lucidity as he was slowly dragged under the ice cold liquid, and he fought to remain on land. The movement triggered more Inferi to rise from the depths of the lake, and in a few moments, Regulus was surrounded by glistening, dirty, cold bodies that wanted nothing more than to drag him down to the depths from whence they came.

Regulus's life did not flash in front of him as he came to terms with his mortality. He was going to die, and there was no stopping it. He screamed at Kreacher to get out of the cave, and watched till his tiny companion disappeared, satisfied that he had at least saved one life. His brother's face flashed in front of him; Sirius Black, fighting the same fight against Voldemort; the fight that he did not know Regulus had also joined.

To the world, to his brother, he would always be a Death Eater. The thought gave him a surge of anger powerful enough to regain his bearings for a fraction of a second. He whipped out his wand, and conjured a circle of fire; waist-deep in water, surrounded by Inferi; a lone eighteen year old, alone in the cave, he felt almost hopeful, when a hand closed around his ankle.

Try as he might, he was no match for the force with which he was pulled underwater. The raging fire sputtered to nothingness, as the wizard that had conjured it gasped for air, lungs filling with ice, eyes tinged red; until finally, with one last feeble breath, he stopped fighting.

Regulus Arcturus Black sank into the depths of the icy blackness, forever cursed to guard the secret of the man who had, essentially, murdered him in cold blood.